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Sample records for fluids magneto-rheological suspensions

  1. A New Generation of Magneto-Rheological Fluid Dampers

    Science.gov (United States)

    2007-11-02

    active MRF damper. An Instron 8821S servo-hydraulic system is used to provide the input road profile. The actuator of the hydraulic unit is mounted...Presented at 8th International conference on Electrorheological (ER) Fluid and Magneto-rheological (MR) Suspensions, Nice, July 9- 13,2001 9...representing the excitation due to the road profile Instron Hydraulic Actuator Linear Slide System providing the movement of the masses 56 0 0.5 1

  2. A magneto rheological hybrid damper for railway vehicles suspensions

    Directory of Open Access Journals (Sweden)

    Gheorghe GHITA

    2012-09-01

    Full Text Available High speed railway vehicles features a specific lateral oscillation resulting from the coupled lateral displacement and yaw of the wheelset which leads to a sinusoid movement of the wheelset along the track, transferred to the entire vehicle. The amplitude of this oscillation is strongly dependant on vehicle’s velocity. Over a certain value, namely the critical speed, the instability phenomenon so-called hunting occurs. To raise the vehicle’s critical speed different designs of the suspension all leading to a much stiffer vehicle can be envisaged. Different simulations prove that a stiffer central suspension will decrease the passenger’s comfort in terms of lateral accelerations of the carboy. The authors propose a semi-active magneto rheological suspension to improve the vehicle’s comfort at high speeds. The suspension has as executive elements hybrid magneto rheological dampers operating under sequential control strategy type balance logic. Using an original mathematical model for the lateral dynamics of the vehicle the responses of the system with passive and semi-active suspensions are simulated. It is shown that the semi-active suspension can improve the vehicle performances.

  3. Super-strong magneto-rheological fluids

    Science.gov (United States)

    Tao, R.

    2001-03-01

    A typical MR fluid is a suspension of magnetic particles of micrometer size in a liquid. Upon application of a strong magnetic field, the fluid turns into a solid. This process is reversible and the response time is of milliseconds. MR fluids presently have a yield shear stress around 80 kPa, which is adequate for applications in shock absorbers and vibration dampers, but is inadequate for automobile clutch etc. Efforts in searching for new materials in the past decades came with limited results. Thus we have developed a new approach to change the microstructure of MR fluids and make them super-strong. It is well known that under a strong magnetic field, the ideal structure of MR fluids is a body-centered tetragonal (bct) lattice. The mechanical strength of MR fluids strongly depends on the microstructure. A bct-lattice based thick column has a much higher yield stress than a single-chain structure. When a magnetic field is applied to a MR fluid, the particles first form chains. With time, the chains may aggregate into columns. However, the unassisted aggregation is not very useful, as it is slow and produces columns with a limited thickness. Our method is based on assisted aggregations. Immediately after a magnetic field is applied, we compress the MR fluid in the field direction before a shear force is applied. The compression pushes the induced chains together to form thick columns. This microstructure change greatly enhances the yield stress. The experiment on an iron-based MR fluid finds 800 kPa for the yield stress, ten times stronger than that without the compression. When the magnetic field is removed, the MR fluid still returns to the liquid state quickly. The upper limit of this structure-enhanced yield stress seems well above 800 kPa. The super-strong MR fluids are suitable for many industrial applications. *Supported by NSF Grant 0196022

  4. A disc-type magneto-rheologic fluid damper

    Institute of Scientific and Technical Information of China (English)

    祝长生

    2003-01-01

    A disc-type magneto-rheological fluid damper operating in shear mode is proposed in this paper,which is based on the special characteristics of the magneto-rheological (MR) fluid with rapid, reversible and dramatic change in its rheological properties by the application of an external magnetic field. The magneticfield of the disc-type MR fluid damper is analysed by the finite element method ; the controllability of the disctype MR fluid damper on the dynamic behaviour of a rotor system ; and the effectiveness of the disc-type MR fluid damper in controlling the vibration of a rotor system, are studied in a flexible rotor system with an over-hung disc. It is shown that the magnetic flux density of the disc-type MR fluid damper in the working areas can significantly change with the applied current in the coil ; and that the dynamic behavior of the disc-type MR fluid damper can be varied by the application of an external magnetic field produced by a low voltage electromagnetic coil. The disc-type MR fluid damper can significantly change the dynamic characteristics of a rotor system, provided that the location of the disk-type MR fluid damper is carefully chosen. The disc-type MR fluid damper is a new actuator with good dynamic characteristics for rotating machinery.

  5. A disc-type magneto-rheologic fluid damper

    Institute of Scientific and Technical Information of China (English)

    祝长生

    2003-01-01

    A disc-type magneto-rheological fluid damper operating in shear mode is proposed in this paper, which is based on the special characteristics of the magneto-rheological (MR) fluid with rapid, reversible and dramatic change in its rheological properties by the application of an external magnetic field. The magnetic field of the disc-type MR fluid damper is analysed by the finite element method; the controllability of the disc-type MR fluid damper on the dynamic behaviour of a rotor system; and the effectiveness of the disc-type MR fluid damper in controlling the vibration of a rotor system, are studied in a flexible rotor system with an over-hung disc. It is shown that the magnetic flux density of the disc-type MR fluid damper in the working areas can significantly change with the applied current in the coil; and that the dynamic behavior of the disc-type MR fluid damper can be varied by the application of an external magnetic field produced by a low voltage electromagnetic coil. The disc-type MR fluid damper can significantly change the dynamic characteristics of a rotor system, provided that the location of the disk-type MR fluid damper is carefully chosen. The disc-type MR fluid damper is a new actuator with good dynamic characteristics for rotating machinery.

  6. Vibration control of a semi-active railway vehicle suspension with magneto-rheological dampers

    Directory of Open Access Journals (Sweden)

    Jong-Seok Oh

    2016-04-01

    Full Text Available This article presents vibration control performances of a semi-active railway vehicle suspension system using a magneto-rheological damper tested on the roller rig. In order to evaluate control performances, a mathematical railway vehicle model with 15 degrees of freedom is first derived to represent the lateral, yaw and roll motions of the car body, bogie frame, and wheel set, respectively. Based on the formulated model, the design parameters of magneto-rheological damper are determined to undertake a compatible comparison with dynamic performances of conventional (existing passive railway vehicle suspension system. The designed magneto-rheological damper is manufactured and its field-dependent damping force characteristics are experimentally evaluated. Subsequently, in order to enhance the ride quality of a railway vehicle suspension equipped with magneto-rheological damper, a skyhook controller associated with an extended Kalman filter is designed in a state space representation. The railway suspension system incorporated with the car body and two bogies is then experimentally set up on the roller rig in order to evaluate the ride quality. It is demonstrated from experimental realization of the controller that the ride quality of the suspension system with magneto-rheological damper can be significantly enhanced compared with the existing passive suspension system.

  7. Structure Analysis for a New Type of Vane Hydraulic Damper Using Magneto-rheological Fluid

    Institute of Scientific and Technical Information of China (English)

    ZHANG Jin-qiu; FENG Zhan-zong; WANG Hong-tao

    2008-01-01

    Over recent years the progress in actuator and microelectronics technology has made intelligent suspension systems feasible. Based on conventional vane hydraulic damper, a new vane magneto-rheological fluid (MRF) damper with fail-safe capability is designed. Firstly, the mathematical model of damping moment is deduced based on the parallel-plate model and Bingham model of MR fluids. Secondly, some influence factors of damping adjustable multiple are analyzed to provide some ways for augmenting the damping adjustable multiple under the condition of keeping initial damping moment invariable. Finally, the magnetic circuit is designed, and magnetic field distribution is simulated with the magnetic finite element analysis software-AN,SOFT. The theory and simulation results confirm that the damping adjustable range of vane MRF damper can meet the requirement of heavy vehiele semi-active suspension system.

  8. A fully dynamic magneto-rheological fluid damper model

    Science.gov (United States)

    Jiang, Z.; Christenson, R. E.

    2012-06-01

    Control devices can be used to dissipate the energy of a civil structure subjected to dynamic loading, thus reducing structural damage and preventing failure. Semiactive control devices have received significant attention in recent years. The magneto-rheological (MR) fluid damper is a promising type of semiactive device for civil structures due to its mechanical simplicity, inherent stability, high dynamic range, large temperature operating range, robust performance, and low power requirements. The MR damper is intrinsically nonlinear and rate-dependent, both as a function of the displacement across the MR damper and the command current being supplied to the MR damper. As such, to develop control algorithms that take maximum advantage of the unique features of the MR damper, accurate models must be developed to describe its behavior for both displacement and current. In this paper, a new MR damper model that includes a model of the pulse-width modulated (PWM) power amplifier providing current to the damper, a proposed model of the time varying inductance of the large-scale 200 kN MR dampers coils and surrounding MR fluid—a dynamic behavior that is not typically modeled—and a hyperbolic tangent model of the controllable force behavior of the MR damper is presented. Validation experimental tests are conducted with two 200 kN large-scale MR dampers located at the Smart Structures Technology Laboratory (SSTL) at the University of Illinois at Urbana-Champaign and the Lehigh University Network for Earthquake Engineering Simulation (NEES) facility. Comparison with experimental test results for both prescribed motion and current and real-time hybrid simulation of semiactive control of the MR damper shows that the proposed MR damper model can accurately predict the fully dynamic behavior of the large-scale 200 kN MR damper.

  9. Nonlinear Dynamics Analysis of the Semiactive Suspension System with Magneto-Rheological Damper

    Directory of Open Access Journals (Sweden)

    Hailong Zhang

    2015-01-01

    Full Text Available This paper examines dynamical behavior of a nonlinear oscillator which models a quarter-car forced by the road profile. The magneto-rheological (MR suspension system has been established, by employing the modified Bouc-Wen force-velocity (F-v model of magneto-rheological damper (MRD. The possibility of chaotic motions in MR suspension is discovered by employing the method of nonlinear stability analysis. With the bifurcation diagrams and corresponding Lyapunov exponent (LE spectrum diagrams detected through numerical calculation, we can observe the complex dynamical behaviors and oscillating mechanism of alternating periodic oscillations, quasiperiodic oscillations, and chaotic oscillations with different profiles of road excitation, as well as the dynamical evolutions to chaos through period-doubling bifurcations, saddle-node bifurcations, and reverse period-doubling bifurcations.

  10. Magneto-rheological defects and failures: A review

    Science.gov (United States)

    Wahid, SA; Ismail, I.; Aid, S.; Rahim, MSA

    2016-02-01

    Magneto-rheological fluid is the colloidal suspension of micron sized magnetic particles in a carrier fluid where defects and failures occur at many circumstances. This paper presents a review on defects and failures of magneto-rheological fluid in engineering applications. The most significant defect is hard cake which developed due to re-dispersion difficulties of remnant particles magnetization, leaving the magneto-rheological fluid ineffective. Clumping effect on the other hand is a separation of carrier fluid from the magnetic particles when magneto-rheological fluid is being exposed to higher magnetic field for an extended period of time. As clumping occurred, it leads to Fluid Particle Separation (FPS) which is believed altering the strength distribution of magneto-rheological fluid and therefore reducing the squeezing force. Another significant failure is magnetic particles oxidation of the magneto-rheological fluid. This paper also will discuss on stability problems which is the most challenged issue in magneto-rheological fluid technology. With the comprehensive review in this paper, researcher can design materials of magneto-rheological fluid for better properties.

  11. Semi-active sliding mode control of vehicle suspension with magneto-rheological damper

    Science.gov (United States)

    Zhang, Hailong; Wang, Enrong; Zhang, Ning; Min, Fuhong; Subash, Rakheja; Su, Chunyi

    2015-01-01

    The vehicle semi-active suspension with magneto-rheological damper(MRD) has been a hot topic since this decade, in which the robust control synthesis considering load variation is a challenging task. In this paper, a new semi-active controller based upon the inverse model and sliding mode control (SMC) strategies is proposed for the quarter-vehicle suspension with the magneto-rheological (MR) damper, wherein an ideal skyhook suspension is employed as the control reference model and the vehicle sprung mass is considered as an uncertain parameter. According to the asymptotical stability of SMC, the dynamic errors between the plant and reference systems are used to derive the control damping force acquired by the MR quarter-vehicle suspension system. The proposed modified Bouc-wen hysteretic force-velocity ( F- v) model and its inverse model of MR damper, as well as the proposed continuous modulation (CM) filtering algorithm without phase shift are employed to convert the control damping force into the direct drive current of the MR damper. Moreover, the proposed semi-active sliding mode controller (SSMC)-based MR quarter-vehicle suspension is systematically evaluated through comparing the time and frequency domain responses of the sprung and unsprung mass displacement accelerations, suspension travel and the tire dynamic force with those of the passive quarter-vehicle suspension, under three kinds of varied amplitude harmonic, rounded pulse and real-road measured random excitations. The evaluation results illustrate that the proposed SSMC can greatly suppress the vehicle suspension vibration due to uncertainty of the load, and thus improve the ride comfort and handling safety. The study establishes a solid theoretical foundation as the universal control scheme for the adaptive semi-active control of the MR full-vehicle suspension decoupled into four MR quarter-vehicle sub-suspension systems.

  12. Semi-active Sliding Mode Control of Vehicle Suspension with Magneto-rheological Damper

    Institute of Scientific and Technical Information of China (English)

    ZHANG Hailong; WANG Enrong; ZHANG Ning; MIN Fuhong; SUBASH Rakheja; SU Chunyi

    2015-01-01

    The vehicle semi-active suspension with magneto-rheological damper(MRD) has been a hot topic since this decade, in which the robust control synthesis considering load variation is a challenging task. In this paper, a new semi-active controller based upon the inverse model and sliding mode control (SMC) strategies is proposed for the quarter-vehicle suspension with the magneto-rheological (MR) damper, wherein an ideal skyhook suspension is employed as the control reference model and the vehicle sprung mass is considered as an uncertain parameter. According to the asymptotical stability of SMC, the dynamic errors between the plant and reference systems are used to derive the control damping force acquired by the MR quarter-vehicle suspension system. The proposed modified Bouc-wen hysteretic force-velocity (F-v) model and its inverse model of MR damper, as well as the proposed continuous modulation (CM) filtering algorithm without phase shift are employed to convert the control damping force into the direct drive current of the MR damper. Moreover, the proposed semi-active sliding mode controller (SSMC)-based MR quarter-vehicle suspension is systematically evaluated through comparing the time and frequency domain responses of the sprung and unsprung mass displacement accelerations, suspension travel and the tire dynamic force with those of the passive quarter-vehicle suspension, under three kinds of varied amplitude harmonic, rounded pulse and real-road measured random excitations. The evaluation results illustrate that the proposed SSMC can greatly suppress the vehicle suspension vibration due to uncertainty of the load, and thus improve the ride comfort and handling safety. The study establishes a solid theoretical foundation as the universal control scheme for the adaptive semi-active control of the MR full-vehicle suspension decoupled into four MR quarter-vehicle sub-suspension systems.

  13. A nonlinear kinematic and dynamic modeling of Macpherson suspension systems with a magneto-rheological damper

    Science.gov (United States)

    Dutta, Saikat; Choi, Seung-Bok

    2016-03-01

    It is well known that Macpherson strut suspension systems are widely used in light and medium weight vehicles. The performance of these suspension systems can be enriched by incorporating magneto-rheological (MR) dampers and an appropriate dynamic model is required in order to find out the ride comfort and other performances properly in the sense of practical environment conditions. Therefore, in this work the kinematic and dynamic modeling of Macpherson strut suspension system with MR damper is presented and its responses are evaluated. The governing equations are formulated using the kinematic properties of the suspension system and adopting Lagrange’s equation. In the formulation of the model, both the rotation of the wheel assembly and the lateral stiffness of the tire are considered to represent the nonlinear characteristic of Macpherson type suspension system. The formulated mathematical model is then compared with equivalent conventional quarter car suspension model and the different dynamic responses such as the displacement of the sprung mass are compared to emphasize the effectiveness of the proposed model. Additionally, in this work the important kinematic properties of suspension system such as camber angle, king-pin angle and track width alteration, which cannot be obtained from conventional quarter car suspension model, are evaluated in time and frequency domains. Finally, vibration control responses of the proposed suspension system are presented in time and frequency domains which are achieved from the semi-active sky-hook controller.

  14. Dynamic analysis of electro- and magneto-rheological fluid dampers using duct flow models

    Science.gov (United States)

    Esteki, Kambiz; Bagchi, Ashutosh; Sedaghati, Ramin

    2014-03-01

    Magneto-rheological (MR) and electro-rheological (ER) fluid dampers provide a semi-active control mechanism for suppressing vibration responses of a structure. MR and ER fluids change their viscosity under the influence of magnetic and electrical fields, respectively, which facilitates automatic control when these fluids are used in damping devices. The existing models, namely the phenomenological models for simulating the behavior of MR and ER dampers, rely on various parameters determined experimentally by the manufacturers for each damper configuration. It is of interest to develop mechanistic models of these dampers which can be applied to various configurations so that their fundamental characteristics can be studied to develop flexible design solutions for smart structures. This paper presents a formulation for dynamic analysis of electro-rheological (ER) and magneto-rheological (MR) fluid dampers in flow and mix mode configurations under harmonic and random excitations. The procedure employs the vorticity transport equation and the regularization function to deal with the unsteady flow and nonlinear behavior of ER/MR fluid in general motion. The finite difference method has been used to solve the governing differential equations. Using the developed approach, the damping force of ER/MR dampers can be calculated under any type of excitation.

  15. Optimization of Magneto-Rheological Damper for Maximizing Magnetic Flux Density in the Fluid Flow Gap Through FEA and GA Approaches

    Science.gov (United States)

    Krishna, Hemanth; Kumar, Hemantha; Gangadharan, Kalluvalappil

    2016-06-01

    A magneto rheological (MR) fluid damper offers cost effective solution for semiactive vibration control in an automobile suspension. The performance of MR damper is significantly depends on the electromagnetic circuit incorporated into it. The force developed by MR fluid damper is highly influenced by the magnetic flux density induced in the fluid flow gap. In the present work, optimization of electromagnetic circuit of an MR damper is discussed in order to maximize the magnetic flux density. The optimization procedure was proposed by genetic algorithm and design of experiments techniques. The result shows that the fluid flow gap size less than 1.12 mm cause significant increase of magnetic flux density.

  16. Optimization of Magneto-Rheological Damper for Maximizing Magnetic Flux Density in the Fluid Flow Gap Through FEA and GA Approaches

    Science.gov (United States)

    Krishna, Hemanth; Kumar, Hemantha; Gangadharan, Kalluvalappil

    2017-08-01

    A magneto rheological (MR) fluid damper offers cost effective solution for semiactive vibration control in an automobile suspension. The performance of MR damper is significantly depends on the electromagnetic circuit incorporated into it. The force developed by MR fluid damper is highly influenced by the magnetic flux density induced in the fluid flow gap. In the present work, optimization of electromagnetic circuit of an MR damper is discussed in order to maximize the magnetic flux density. The optimization procedure was proposed by genetic algorithm and design of experiments techniques. The result shows that the fluid flow gap size less than 1.12 mm cause significant increase of magnetic flux density.

  17. Hysteresis-induced bifurcation and chaos in a magneto-rheological suspension system under external excitation

    Science.gov (United States)

    Hailong, Zhang; Enrong, Wang; Fuhong, Min; Ning, Zhang

    2016-03-01

    The magneto-rheological damper (MRD) is a promising device used in vehicle semi-active suspension systems, for its continuous adjustable damping output. However, the innate nonlinear hysteresis characteristic of MRD may cause the nonlinear behaviors. In this work, a two-degree-of-freedom (2-DOF) MR suspension system was established first, by employing the modified Bouc-Wen force-velocity (F-v) hysteretic model. The nonlinear dynamic response of the system was investigated under the external excitation of single-frequency harmonic and bandwidth-limited stochastic road surface. The largest Lyapunov exponent (LLE) was used to detect the chaotic area of the frequency and amplitude of harmonic excitation, and the bifurcation diagrams, time histories, phase portraits, and power spectrum density (PSD) diagrams were used to reveal the dynamic evolution process in detail. Moreover, the LLE and Kolmogorov entropy (K entropy) were used to identify whether the system response was random or chaotic under stochastic road surface. The results demonstrated that the complex dynamical behaviors occur under different external excitation conditions. The oscillating mechanism of alternating periodic oscillations, quasi-periodic oscillations, and chaotic oscillations was observed in detail. The chaotic regions revealed that chaotic motions may appear in conditions of mid-low frequency and large amplitude, as well as small amplitude and all frequency. The obtained parameter regions where the chaotic motions may appear are useful for design of structural parameters of the vibration isolation, and the optimization of control strategy for MR suspension system. Projects supported by the National Natural Science Foundation of China (Grant Nos. 51475246, 51277098, and 51075215), the Research Innovation Program for College Graduates of Jiangsu Province China (Grant No. KYLX15 0725), and the Natural Science Foundation of Jiangsu Province of China (Grant No. BK20131402).

  18. Smart mouse: 5-DOF haptic hand master using magneto-rheological fluid actuators

    Science.gov (United States)

    Kim, K. H.; Nam, Y. J.; Yamane, R.; Park, M. K.

    2009-02-01

    This paper is concerned with a haptic hand master intended to display force feedback at the fingertip of the human user. The haptic hand master, named 'Smart Mouse' has two significant differences from previous other hand masters: actuators and structure. Five passive actuators featured with magneto-rheological fluid are used to ensure the interface safety and the control stability. In order to eliminate the unnecessary reaction force and reduce muscular fatigue during operating, the mouse-like structure is adapted. Also, two assumptions are proposed for the simplicity of its kinematics and manufacturing; one is that the fingertips lies on a plane during grasping the objects, and the other is that the equilibrium point of the fingertip reaction forces is in the object. Due to these characteristics, the human hand operating the smart mouse has the kinematic configuration similar to a 5-DOF parallel manipulator.

  19. Smart mouse: 5-DOF haptic hand master using magneto-rheological fluid actuators

    Energy Technology Data Exchange (ETDEWEB)

    Kim, K H; Nam, Y J; Park, M K [Graduated School of Mechanical Engineering, Pusan National University, Busan 609-735 (Korea, Republic of); Yamane, R [Kokushikan University, 4-28-1 Setagaya, Setagaya-ku, Tokyo 154-8515 (Japan)], E-mail: mkpark1@pusan.ac.kr

    2009-02-01

    This paper is concerned with a haptic hand master intended to display force feedback at the fingertip of the human user. The haptic hand master, named 'Smart Mouse' has two significant differences from previous other hand masters: actuators and structure. Five passive actuators featured with magneto-rheological fluid are used to ensure the interface safety and the control stability. In order to eliminate the unnecessary reaction force and reduce muscular fatigue during operating, the mouse-like structure is adapted. Also, two assumptions are proposed for the simplicity of its kinematics and manufacturing; one is that the fingertips lies on a plane during grasping the objects, and the other is that the equilibrium point of the fingertip reaction forces is in the object. Due to these characteristics, the human hand operating the smart mouse has the kinematic configuration similar to a 5-DOF parallel manipulator.

  20. Synthesis and characterization of magneto-rheological (MR fluids for MR brake application

    Directory of Open Access Journals (Sweden)

    Bhau K. Kumbhar

    2015-09-01

    Full Text Available Magneto rheological (MR fluid technology has been proven for many industrial applications like shock absorbers, actuators, etc. MR fluid is a smart material whose rheological characteristics change rapidly and can be controlled easily in presence of an applied magnetic field. MR brake is a device to transmit torque by the shear stress of MR fluid. However, MR fluids exhibit yield stress of 50–90 kPa. In this research, an effort has been made to synthesize MR fluid sample/s which will typically meet the requirements of MR brake applications. In this study, various electrolytic and carbonyl iron powder based MR fluids have been synthesized by mixing grease as a stabilizer, oleic acid as an antifriction additive and gaur gum powder as a surface coating to reduce agglomeration of the MR fluid. MR fluid samples based on sunflower oil, which is bio-degradable, environmentally friendly and abundantly available have also been synthesized. These MR fluid samples are characterized for determination of magnetic, morphological and rheological properties. This study helps identify most suitable localized MR fluid meant for MR brake application.

  1. SEMI-ACTIVE CONTROL OF VEHICLE SUSPENSION WITH MAGNETO- RHEOLOGICAL DAMPERS: PART Ⅰ-CONTROLLER SYNTHESIS AND EVALUATION

    Institute of Scientific and Technical Information of China (English)

    WANG Enrong; YING Liang; WANG Wanjun; RAKHEJA Subhash; SU Chunyi

    2008-01-01

    A modified skyhook-based semi-active controller is proposed for implementing an asymmetric control suspension design with symmetric magneto-rheological (MR) dampers. The controller is formulated in current form, which is modulated by integrating a continuous modulation and an asymmetric damping force generation algorithms, so as to effectively minimize switching and hysteretic effects from the MR-damper. The proposed controller is implemented with a quarter-vehicle MR-suspension model, and its relative response characteristics are thus evaluated in terms of defined performance measures under varying amplitude harmonic, rounded pulse and random excitations. The sensitivity of the semi-active suspension performance to variations in controller parameters is thoroughly evaluated. The results illustrate that the proposed skyhook-based asymmetric semi-active MR-suspension controller has superior robustness on the system parameter variations, and can achieve desirable multi-objective suspension performance.

  2. A magneto-rheological fluid mount featuring squeeze mode: analysis and testing

    Science.gov (United States)

    Chen, Peng; Bai, Xian-Xu; Qian, Li-Jun; Choi, Seung-Bok

    2016-05-01

    This paper presents a mathematical model for a new semi-active vehicle engine mount utilizing magneto-rheological (MR) fluids in squeeze mode (MR mount in short) and validates the model by comparing analysis results with experimental tests. The proposed MR mount is mainly comprised of a frame for installation, a main rubber, a squeeze plate and a bobbin for coil winding. When the magnetic fields on, MR effect occurs in the upper gap between the squeeze plate and the bobbin, and the dynamic stiffness can be controlled by tuning the applied currents. Employing Bingham model and flow properties between parallel plates of MR fluids, a mathematical model for the squeeze type of MR mount is formulated with consideration of the fluid inertia, MR effect and hysteresis property. The field-dependent dynamic stiffness of the MR mount is then analyzed using the established mathematical model. Subsequently, in order to validate the mathematical model, an appropriate size of MR mount is fabricated and tested. The field-dependent force and dynamic stiffness of the proposed MR mount are evaluated and compared between the model and experimental tests in both time and frequency domains to verify the model efficiency. In addition, it is shown that both the damping property and the stiffness property of the proposed MR mount can be simultaneously controlled.

  3. Semi-active engine mount design using auxiliary magneto-rheological fluid compliance chamber

    Science.gov (United States)

    Mansour, H.; Arzanpour, S.; Golnaraghi, M. F.; Parameswaran, A. M.

    2011-03-01

    Engine mounts are used in the automotive industry to isolate engine and chassis by reducing the noise and vibration imposed from one to the other. This paper describes modelling, simulation and design of a semi-active engine mount that is designed specifically to address the complicated vibration pattern of variable displacement engines (VDE). The ideal isolation for VDE requires the stiffness to be switchable upon cylinder activation/deactivation operating modes. In order to have a modular design, the same hydraulic engine mount components are maintained and a novel auxiliary magneto-rheological (MR) fluid chamber is developed and retrofitted inside the pumping chamber. The new compliance chamber is a controllable pressure regulator, which can effectively alter the dynamic performance of the mount. Switching between different modes happens by turning the electrical current to the MR chamber magnetic coil on and off. A model has been developed for the passive hydraulic mount and then it is extended to include the MR auxiliary chamber as well. A proof-of-concept prototype of the design has been fabricated which validates the mathematical model. The results demonstrate unique capability of the developed semi-active mount to be used for VDE application.

  4. A comparative work on vibration control of a quarter car suspension system with two different magneto-rheological dampers

    Science.gov (United States)

    Park, Jhin Ha; Kim, Wan Ho; Shin, Cheol Soo; Choi, Seung-Bok

    2017-01-01

    This work compares the ride comfort of a passenger vehicle whose suspension system is equipped with two different magneto-rheological (MR) dampers: with and without bypass holes in the piston. In order to achieve this goal, two cylindrical type MR dampers, which otherwise have the same such geometrical dimensions as radius of piston, length of pole and distance between two poles, are designed based on a mathematical model and subsequently manufactured. One of MR dampers is then modified by making bypass holes in the piston bobbin structure to obtain a relatively low slope of damping force in the pre-yield region. The field-dependent damping force characteristics are investigated through both simulation and experiment. After characterizing the field-dependent damping force of the two MR dampers, a quarter car model is established to evaluate the ride comfort. In this work, a simple but very effective sky-hook controller is adopted, and vibration control performance is evaluated under two road profiles: bump and random road excitations. It is demonstrated through simulation and experiment that the MR damper with bypass holes provides better ride comfort to the car so equipped than that without.

  5. Frequency analysis of a semi-active suspension with magneto-rheological dampers

    Science.gov (United States)

    Andronic, Florin; Mihai, Ioan; Suciu, Cornel; Beniuga, Marius

    2015-02-01

    Suspension systems for motor vehicles are constantly evolving in order to ensure vehicle stability and traffic safety under all driving conditions. The present work aims to highlight the influence factors in the case of a quarter car model for semi-active suspensions. The functions that must be met by such suspension systems are first presented. Mathematical models for passive systems are first illustrated and then customized for the semi-active case. A simulation diagram was conceived for Matlab Simulink. The obtained simulation results allow conducting a frequency analysis of the passive and semi-active cases of the quarter car model. Various charts for Passive Suspension Transmissibility and for the Effect of Damping on Vertical Acceleration Response were obtained for both passive and semi-active situations. Analysis of obtained results allowed evaluating of the suspension systems behavior and their frequency dependence. Significant differences were found between the behaviors of passive and semi-active suspensions. It was found that semi-active suspensions ensure damping in accordance to the chosen control method, and are much more efficient than passive ones.

  6. Real-Time Driving Simulation of Magneto-Rheological Active Damper Stryker Suspension

    Science.gov (United States)

    2011-10-24

    driver’s seat location. The Belgian Block terrain was developed using Non Uniform Rational B-Spline ( NURBS ), discussed next in more detail. Though...suspensions. For the Munson Gravel course a bump mapping technique utilizing Non-Uniform Rational B-Spline ( NURBS ) was used to produce road roughness...representative of a gravel road. The NURBS were generated using the root mean square for the gravel road. 5. RIDE DEMONSTRATION RESULTS A team of

  7. Regime of aggregate structures and magneto-rheological characteristics of a magnetic rod-like particle suspension: Monte Carlo and Brownian dynamics simulations

    Science.gov (United States)

    Okada, Kazuya; Satoh, Akira

    2017-09-01

    In the present study, we address a suspension composed ferromagnetic rod-like particles to elucidate a regime change in the aggregate structures and the magneto-rheological characteristics. Monte Carlo simulations have been employed for investigating the aggregate structures in thermodynamic equilibrium, and Brownian dynamics simulations for magneto-rheological features in a simple shear flow. The main results obtained here are summarized as follows. For the case of thermodynamic equilibrium, the rod-like particles aggregate to form thick chain-like clusters and the neighboring clusters incline in opposite directions. If the external magnetic field is increased, the thick chain-like clusters in the magnetic field direction grow thicker by adsorbing the neighboring clusters that incline in the opposite direction. Hence, a significant phase change in the particle aggregates is not induced by an increase in the magnetic field strength. For the case of a simple shear flow, even a weak shear flow induces a significant regime change from the thick chain-like clusters of thermodynamic equilibrium into wall-like aggregates composed of short raft-like clusters. A strong external magnetic field drastically changes these aggregates into wall-like aggregates composed of thick chain-like clusters rather than the short raft-like clusters. The internal structure of these aggregates is not strongly influenced by a shear flow, and the formation of the short raft-like clusters is maintained inside the aggregates. The main contribution to the net viscosity is the viscosity component due to magnetic particle-particle interaction forces in relation to the present volumetric fraction. Hence, a larger magnetic interaction strength and also a stronger external magnetic field give rise to a larger magneto-rheological effect. However, the dependence of the viscosity on these factors is governed in a complex manner by whether or not the wall-like aggregates are composed mainly of short raft

  8. Theoretical and experimental study of magneto-rheological fluid disc brake

    Directory of Open Access Journals (Sweden)

    E.M. Attia

    2017-06-01

    The fluid is inserted between the rotating and fixed discs and a magnetic field is imposed on the fluid. In this paper, a complete test rig for an MR fluid disc brake is introduced. Experiments are conducted to measure the braking torque and speed of shaft during braking process and the results are presented at different voltage input to the brake. Also theoretical analysis for both MR brake and the mechanical system is developed and is solved numerically using finite difference method and Matlab software. Effect of current input to the MR brake, viscosity of fluid and design parameters is taken into consideration. A validation of the theoretical results with CFD model is introduced. The experimental results are performed and both angular velocity and the braking torque are obtained as responses during the braking process. A comparison between braking torques obtained from theoretical and experimental work shows agreement when voltage is 2 V at speed of 150 rpm and also agreement when voltage is 2 and 3 V at speed of 250 rpm.

  9. Torque Control of a Rehabilitation Teaching Robot Using Magneto-Rheological Fluid Clutches

    Science.gov (United States)

    Hakogi, Hokuto; Ohaba, Motoyoshi; Kuramochi, Naimu; Yano, Hidenori

    A new robot that makes use of MR-fluid clutches for simulating torque is proposed to provide an appropriate device for training physical therapy students in knee-joint rehabilitation. The feeling of torque provided by the robot is expected to correspond to the torque performance obtained by physical therapy experts in a clinical setting. The torque required for knee-joint rehabilitation, which is a function of the rotational angle and the rotational angular velocity of a knee movement, is modeled using a mechanical system composed of typical spring-mass-damper elements. The robot consists of two MR-fluid clutches, two induction motors, and a feedback control system. In the torque experiments, output torque is controlled using the spring and damper coefficients separately. The values of these coefficients are determined experimentally. The experimental results show that the robot would be suitable for training physical therapy students to experience similar torque feelings as needed in a clinical situation.

  10. Modeling and characterization of a magneto-rheological fluid based damper and analysis of vibration isolation with the damper operating in passive mode

    Science.gov (United States)

    Dutta, Saikat; Chakraborty, G.

    2015-09-01

    A physical model of a type of commercially available magneto-rheological fluid based damper has been developed to study the input-output response characteristics. The impedance of the nonlinear device has been analyzed based on equivalent linearization method. The capability of isolating vibration with the help of such a damper has also been studied analytically. The damper is operated in passive mode while the excitation is kept harmonic. A novel method of obtaining the steady-state response of a damped oscillator is presented that uses a combination of harmonic balance method and the method of averaging. The isolating property of the damper has been measured by transmissibilities derived for equivalent linear system.

  11. Design and Simulation of a Multi-cylindrical Magneto-rheological Fluid Clutch%多筒式磁流变液离合器的设计及仿真

    Institute of Scientific and Technical Information of China (English)

    2015-01-01

    为满足 B 级轿车大转矩传递的要求,并克服高速旋转工况下离心力对磁流变液(Magneto-Rheological Fluid, MRF)的影响,提出了多筒式磁流变液离合器(Magneto-rheological Fluid Clutch,MFC)结构型式,设计了可以自动消除因工作温度变化导致磁流变液膨胀或收缩的压力平衡机构;同时,在 Ansoft Maxwell 中建立了离合器有限元分析模型,并对磁力线分布和磁场强度进行了仿真分析。结果表明:当励磁电流在2.5~3 A 之间时即可达到设计要求。%To meet the requirement of transmitting a large torque of B-class automobile and overcome the effects of centrifugal force under high speed rotating conditions on Magneto-Rheological Fluid (MRF),a multi-cylindrical Magneto-rheological Fluid Clutch (MFC)is proposed.A pressure balance mechanism is designed to avoid the expansion or contraction of MRF caused by the temperature changes.A finite ele-ment analysis model is built in Ansoft Maxwell,and the magnetic force line distribution and magnetic field intensity are simulated.The simulation result shows that the design goal can be realized when the excitation current is between 2.5 A and 3 A.

  12. SEMI-ACTIVE CONTROL OF VEHICLE SUSPENSION WITH MAGNETO-RHEOLOGICAL DAMPERS:PART III——EXPERIMENTAL VALIDATION

    Institute of Scientific and Technical Information of China (English)

    WANG Enrong; YING Liang; WANG Wanjun; RAKHEJA Subhash; SU Chunyi

    2008-01-01

    A hardware-in-the-loop (HIL) test and simulation platform is developed in the laboratory, so as to validate the performance characteristics of the proposed skyhook-based asymmetric semi-active controller in Part I, and examine the validity of the proposed MR-damper model in a system surrounding. A real-time monitor is designed to assess and monitor the responses of the quarter-vehicle model in the HIL platform, and to select the excitation, controller synthesis, and the output displays. A drive current circuit hardware employing PID feedback technique is developed to compensate for the time delays from the servo-controller and drive current circuit, in which a small resistance is integrated in the current amplifier circuit to provide the feedback signal. The experiments were performed to measure the responses of the quarter-vehicle MR-suspension models with fixed current and the proposed semi-active MR-damping variations, under harmonic, rounded pulse and random road excitations. The measured data were compared with the corresponding model results to examine the model and controller validity, and revealed generally good agreements in the model and tested results and very little sensitivity of the tested responses to variations in the sprung mass. The HIL test results validate the effectiveness of the proposed skyhook-based semi-active asymmetric controller and its high robustness against the vehicle load variations in view of the intelligent vehicle suspension design.

  13. The effect of the volume fraction and viscosity on the compression and tension behavior of the cobalt-ferrite magneto-rheological fluids

    Directory of Open Access Journals (Sweden)

    H. Shokrollahi

    2016-03-01

    Full Text Available The purpose of this work is to investigate the effects of the volume fraction and bimodal distribution of solid particles on the compression and tension behavior of the Co-ferrite-based magneto-rheological fluids (MRFs containing silicon oil as a carrier. Hence, Co-ferrite particles (CoFe2O4 with two various sizes were synthesized by the chemical co-precipitation method and mixed so as to prepare the bimodal MRF. The X-Ray Diffraction (XRD analysis, Fourier Transform Infrared Spectroscopy (FTIR, Laser Particle Size Analysis (LPSA and Vibrating Sample Magnetometer (VSM were conducted to examine the structural and magnetic properties, respectively. The results indicated that the increase of the volume fraction has a direct increasing influence on the values of the compression and tension strengths of fluids. In addition, the compression and tension strengths of the mixed MRF sample (1.274 and 0.647 MPa containing 60 and 550 nm samples were higher than those of the MRF sample with the same volume fraction and uniform particle size of 550 nm.

  14. The influence of the current intensity on the damping characteristics for a magneto-rheological damper of passenger car

    Science.gov (United States)

    Dobre, A.; Andreescu, C. N.; Stan, C.

    2016-08-01

    Due to their simplicity and controllability, adaptive dampers became very popular in automotive engineering industry, especially in the passenger cars industry, in spite of technological obstacles inherent and the high cost of the magnetic fluid. “MagneRide” is the first technology which uses smart fluids in the shock absorbers of the vehicles adaptive suspensions. Since the discovery of the magneto-rheological effect there is a consistent progress regarding the control algorithms and hardware part itself. These magneto-rheological devices have a major potential which can be explored in various fields of applications. At present many companies make researches for the improvement of the response time and for obtaining a better response at low frequency and amplitude of the body car oscillations. The main objective of this paper is to determine the damping characteristic of a magnetorheological shock absorber of a passenger car. The authors aim to observe how to modify the damping characteristic by changing the intensity of the electric current. The experimental researches have being carried out on a complex and modern test bench especially built for testing shock absorbers, in order to compare the damping characteristic of the classical damper with the magneto-rheological damper.

  15. An innovative multi-gap clutch based on magneto-rheological fluids and electrodynamic effects: magnetic design and experimental characterization

    Science.gov (United States)

    Rizzo, R.

    2017-01-01

    In this paper an innovative multi-gap magnetorheological clutch is described. It is inspired by a device previously developed by the author’s research group and contains a novel solution based on electrodynamic effects, capable to considerably improve the transmissible torque during the engagement phase. Since this (transient) phase is characterized by a non-zero angular speed between the two clutch shafts, the rotation of a permanent magnets system, used to excite the fluid, induces eddy currents on some conductive material strategically positioned in the device. As a consequence, an electromagnetic torque is produced which is added to the torque transmitted by the magnetorheological fluid only. Once the clutch is completely engaged and the relative speed between the two shafts is zero, the electrodynamic effects vanish and the device operates like a conventional magnetorheological clutch. The system is investigated and designed by means a 3D FEM model and the performance of the device is experimentally validated on a prototype.

  16. SEMI-ACTIVE CONTROL OF VEHICLE SUSPENSION WITH MAGNETO-RHEOLOGICAL DAMPERS PART Ⅱ——EVALUATION OF SUSPENSION PERFORMANCE

    Institute of Scientific and Technical Information of China (English)

    WANG Enrong; YING Liang; WANG Wanjun; RAKHEJA Subhash; SU Chunyi

    2008-01-01

    The design and analysis of an intelligent vehicle suspension with MR dampers should address hybrid semi-active control goals, such as rejection of current-switching discontinuity and MR-damper hysteresis, asymmetric damping from the symmetric MR-damper design, robustness on the vehicle operation parameter uncertainties and consideration of essential multiple suspension goals. Following the proposed skyhook-based asymmetric semi-active controller (Part Ⅰ) for achieving the above goals, herein, a set of suspension performance measures and three kinds of varying amplitude harmonic, rounded pulse and really measured random excitations are systematically defined, and the sensitivity of quarter-vehicle MR-suspension performance to variations in operating conditions is thoroughly analyzed. The results illustrate that the proposed skyhook-based semi-active MR-suspension in the asymmetric mode yields relatively superior dynamic responses to meet the multiple suspension performances of ride, rattle space, road-holding and dynamic tire force transmitted to the pavement, and has desirable robustness on variations in operating conditions of vehicle load and speed and the road roughness.

  17. Novel design of a self powered and self sensing magneto-rheological damper

    Science.gov (United States)

    Meftahul Ferdaus, Mohammad; Rashid, M. M.; Bhuiyan, M. M. I.; Muthalif, Asan Gani Bin Abdul; Hasan, M. R.

    2013-12-01

    Magneto-rheological (MR) dampers are semi-active control devices and use MR fluids. Magneto-rheological dampers have successful applications in mechatronics engineering, civil engineering and numerous areas of engineering. At present, traditional MR damper systems, require a isolated power supply and dynamic sensor. This paper presents the achievability and accuracy of a self- powered and self-sensing magneto-rheological damper using harvested energy from the vibration and shock environment in which it is deployed and another important part of this paper is the increased yield stress of the Magneto rheological Fluids. Magneto rheological fluids using replacement of glass beads for Magnetic Particles to surge yield stress is implemented here. Clearly this shows better result on yield stress, viscosity, and settling rate. Also permanent magnet generator (PMG) is designed and attached to a MR damper. For evaluating the self-powered MR damper's vibration mitigating capacity, an Engine Mount System using the MR damper is simulated. The ideal stiffness of the PMG for the Engine Mount System (EMS) is calculated by numerical study. The vibration mitigating performance of the EMS employing the self-powered & self sensing MR damper is theoretically calculated and evaluated in the frequency domain.

  18. A Study on the Simulation of Semi-active Air Suspension with Magneto-rheological Damper%汽车磁流变减振器半主动空气悬架仿真研究

    Institute of Scientific and Technical Information of China (English)

    叶光湖; 吴光强

    2015-01-01

    Based on the stiffness test of air spring, a half vehicle vertical vibration model is established. Then, according to the characteristics of skyhook control and groundhook control, a combined control strategy for semi-active air suspension with magneto-rheological ( MR) damper is designed. The performances of suspension sys-tems with different control strategies are simulated with Matlab/Simulink. The comparison on the results of simula-tions in both time and frequency domains show that with combined control strategy, not only the ride comfort of vehi-cle can be enhanced, but also the handling stability of vehicle can be ensured, leading to the improvement of overall performance of vehicle.%根据空气弹簧刚度试验,建立了1/2汽车垂向振动模型。进而,依据天棚控制和地棚控制特点,设计了汽车磁流变减振器半主动空气悬架综合控制策略。在Matlab/Simulink环境下对带有不同控制策略的悬架系统进行性能仿真。对比时、频域仿真结果表明:采用综合控制策略不仅能提高汽车平顺性,且能保证汽车的操纵稳定性,使车辆综合性能得到改善。

  19. State of the art of control schemes for smart systems featuring magneto-rheological materials

    Science.gov (United States)

    Choi, Seung-Bok; Li, Weihua; Yu, Miao; Du, Haiping; Fu, Jie; Do, Phu Xuan

    2016-04-01

    This review presents various control strategies for application systems utilizing smart magneto-rheological fluid (MRF) and magneto-rheological elastomers (MRE). It is well known that both MRF and MRE are actively studied and applied to many practical systems such as vehicle dampers. The mandatory requirements for successful applications of MRF and MRE include several factors: advanced material properties, optimal mechanisms, suitable modeling, and appropriate control schemes. Among these requirements, the use of an appropriate control scheme is a crucial factor since it is the final action stage of the application systems to achieve the desired output responses. There are numerous different control strategies which have been applied to many different application systems of MRF and MRE, summarized in this review. In the literature review, advantages and disadvantages of each control scheme are discussed so that potential researchers can develop more effective strategies to achieve higher control performance of many application systems utilizing magneto-rheological materials.

  20. An Experimental Study on the Dynamic Characteristics of Vehicle Semi-active Seat Suspension with Magneto-rheological Damper%汽车磁流变半主动座椅悬架动态特性的试验研究

    Institute of Scientific and Technical Information of China (English)

    寇发荣

    2015-01-01

    For further improving vehicle ride comfort,a magneto-rheological damper for vehicle semi-active seat suspension is developed with its damping characteristic test conducted. After analyzing its force bearing condi-tion, a dynamics model for vehicle semi-active seat suspension is built, a corresponding skyhook control strategy is devised, and a simulation is performed on the skyhook control of seat under both random and sinusoidal excitation inputs. Meanwhile a physical prototype of semi-active seat suspension with magneto-rheological damper and its test bench system are developed with corresponding bench test carried out. The results indicate that the results of simu-lation basically well agree with test data and the magneto-rheological damper developed has a good damping control-lability. Compared to original passive seat suspension, the dynamic performances of vehicle semi-active seat with magneto-rheological damper are improved by some 30% with a significant effect of vibration attenuation.%为进一步提高汽车的乘坐舒适性,研发了一种汽车座椅半主动悬架用磁流变减振器,并对其进行阻尼特性试验,通过分析其受力情况,建立了汽车半主动座椅悬架动力学模型,设计了用于座椅磁流变半主动悬架的天棚控制策略,并在随机和正弦激励输入下进行了座椅天棚控制仿真计算,试制了磁流变半主动座椅物理样机及试验台架系统,开展了磁流变半主动座椅悬架的台架试验研究。结果表明,理论仿真和试验结果基本吻合,磁流变减振器阻尼可控性好;相对于被动座椅悬架,采用磁流变半主动座椅悬架后,座椅动态性能改善了30%左右,磁流变半主动座椅悬架减振效果显著。

  1. Tribological effects of particle concentration of an iron particle suspension

    Institute of Scientific and Technical Information of China (English)

    W.C.Leung; P.L.Wong; C.Feng; W.A.Bullough

    2001-01-01

    The general friction and wear performance of an iron particulate suspension underboundary lubrication conditions are presented. The suspension is a mixture of 1-5 micrometerdiameter carbonyl iron particles with commercial hydraulic oil, which resembles typical compositionof magneto-rheological fluids. The investigation involves changing the particle concentration of thesuspension. The optimal concentration of the suspension from a tribological view point can be ob-served from the experimental results,which provides a reference to the design of the particle load-ing of magneto-rheological fluids.

  2. Vibration control of a structure using Magneto-Rheological grease damper

    Science.gov (United States)

    Sugiyama, Shinya; Sakurai, Tomoki; Morishita, Shin

    2013-09-01

    This paper describes an application study of Magneto-Rheological (MR) grease damper to a structure with three stories. MR fluid is known as one of successful smart materials whose rheological properties can be varied by magnetic field strength, and has been applied to various kinds of device such as dampers, clutches, engine mounts, etc. However, ferromagnetic particles dispersed in MR fluid settle out of the suspension after a certain interval due to the density difference between the particles and their career fluid. To overcome this defect, we have developed a new type of controllable working fluid using grease as the career of magnetic particles. Network of thickener in grease is expected to hold the magnetic particles and prevent them from settled down. No or little sedimentation was observed in MR grease whose characteristics could be controlled by the magnetic field strength. MR grease was introduced into a cylindrical damper and its performance was studied. As a result, it was confirmed that the damping force of MR grease damper could be controlled by the applied electric current to the coil in the cylinder of damper. Furthermore, vibration response of a three-story model structure equipped with MR grease damper was investigated experimentally, and it was shown that MR grease damper worked effectively as a semi-active damper.

  3. A comparison of field-dependent rheological properties between spherical and plate-like carbonyl iron particles-based magneto-rheological fluids

    Science.gov (United States)

    Tan Shilan, Salihah; Amri Mazlan, Saiful; Ido, Yasushi; Hajalilou, Abdollah; Jeyadevan, Balachandran; Choi, Seung-Bok; Azhani Yunus, Nurul

    2016-09-01

    This work proposes different sizes of the plate-like particles from conventional spherical carbonyl iron (CI) particles by adjusting milling time in the ball mill process. The ball mill process to make the plate-like particles is called a solid-state powder processing technique which involves repeated welding, fracturing and re-welding of powder particles in a high-energy ball mill. The effect of ball milling process on the magnetic behavior of CI particles is firstly investigated by vibrating sample magnetometer. It is found form this investigation that the plate-like particles have higher saturation magnetization (about 8%) than that of the spherical particles. Subsequently, for the investigation on the sedimentation behavior the cylindrical measurement technique is used. It is observed from this measurement that the plate-like particles show slower sedimentation rate compared to the spherical particles indicating higher stability of the MR fluid. The field-dependent rheological properties of MR fluids based on the plate-like particles are then investigated with respect to the milling time which is directly connected to the size of the plate-like particles. In addition, the field-dependent rheological properties such as the yield stress are evaluated and compared between the plate-like particles based MR fluids and the spherical particles based MR fluid. It is found that the yield shear stress of the plate-like particles based MR fluid is increased up to 270% compared to the spherical particles based MR fluid.

  4. Modeling a magneto-rheological soft starter for use with belt conveyors

    Institute of Scientific and Technical Information of China (English)

    Tian Zuzhi; Hou Youfu

    2012-01-01

    The theory of magnetic circuit design,the constitutive equations of a magneto-rheological fluid,and the load properties of belt conveyors were used to design a magneto-rheological soft starter test-bed.The magnetic field distribution in the working gap was analyzed and the current-speed relationship was investigated.A mathematical model for the time response was deduced.The results show that a linear relationship between current and magnetic field is seen when the magnetic materials are not saturated and the magnetic field is uniform in the working section.The rotation speed of the driven shaft changes linearly with increasing time.The response is rapid and can be as short as milliseconds.This meets the starting requirements of belt conveyors.

  5. DEVELOPMENT OF TEST PROTOCOLS FOR THE ANALYSIS OF MAGNETO-RHEOLOGICAL PROPERTIES OF FIELD-RESPONSIVE BITUMINOUS BINDERS

    Directory of Open Access Journals (Sweden)

    Ezio Santagata

    2014-01-01

    Full Text Available Magneto-rheological fluids are materials that exhibit a significant change in their rheological properties in the presence of a magnetic field. Because of such a field-dependent behavior, they can act as smart materials in applications in which changeable performances are desired. In road pavement engineering, the use of bitumen-based magneto-rheological fluids may open innovative scenarios related to the construction of smart pavement sections and to the investigation of damage mechanisms in binders and mixtures. The research work presented in this study explored magneto-rheological properties of several field-responsive bituminous binders obtained from two different base bitumens combined with multi-wall carbon nanotubes and powder iron. The experimental program included oscillatory shear loading tests at different temperatures, performed in the strain controlled mode by means of a dynamic shear rheometer equipped with a magneto-rheological device. The investigation was carried out with the specific goal of identifying critical issues which should be taken into account in materials preparation, testing procedures and data analysis. Undesired overheating of specimens during testing was identified and taken into account for a correct interpretation of experimental data. Thus, while the field-sensitivity of carbon nanotubes was found to be negligible as a result of the magnetic shielding action of bitumen, it was shown that powder iron can significantly affect the magneto-rheological properties of bituminous binders when employed in sufficiently high amounts. Moreover, obtained results indicated that selection of base bitumen is a key factor in designing bituminous-based smart materials. Practical implications which derive from the study are mainly relative to the fine-tuning of laboratory characterization procedures which should necessarily overcome current limitations in temperature regulation and magnetic field generation. Experimental data

  6. Design and analysis of an innovative combined magneto-rheological damper-mount

    Science.gov (United States)

    Phu, Do Xuan; Chung, Jye Ung; Choi, Seung Bok

    2015-04-01

    In this paper, a new innovative modified high-loaded magneto-rheological fluid (MR in short) damper-mount is presented. The proposed damper-mount is designed based on two modes of MR fluid such as flow mode and shear mode, and it includes two separated electric coil for establishing magnetic field. The damping force of the damper-mount is analyzed based on the difference pressure between upper chamber and lower chamber. After analyzing the mathematical function of damping force, the proposed mount is optimized following the maximal damping force by using ANSYS software. Besides, there is a laboratorial MR fluid using in this optimization such as plate-like fluid MRF140. Results of optimization show that the requirement of damping force is obtain and the saturation of materials is in range of limitation.

  7. Numerical Model of a Hybrid Damping System Composed of a Buckling Restrained Brace with a Magneto Rheological Damper

    Directory of Open Access Journals (Sweden)

    Filip-Vacarescu Norin

    2016-03-01

    Full Text Available This paper discusses the concept of a hybrid damper made from a combination of two dissipative devices. A passive hysteretic device like steel Buckling Restrained Brace (BRB can be combined with a magneto-rheological (MR Fluid Damper in order to obtain a hybrid dissipative system. This system can work either as a semi-active system, if the control unit is available, or as a passive system, tuned for working according to performance based seismic engineering (PBSE scale of reference parameters (i.e. interstory drift.

  8. Immune Response Augmentation in Metastasized Breast Cancer by Localized Therapy Utilizing Biocompatible Magnetic Fluids. Addendum

    Science.gov (United States)

    2009-08-01

    research is to assess the efficacy of augmenting immune responses to breast cancer through the use of magneto-rheological fluid (MRF), suspensions of...poly(NIPAAm) onto silica nanoparticles using ATRP has been investigated by [5, 6]. In the present work, MRFs were synthesized from suspensions of...of Iron-Based Nanofluids ”, International Journal of Modern Physics B, Vol. 21, pp. 4774 – 4781, 2007 18. J. P. Jakubovics, “Magnetism and Magnetic

  9. A geometrical optimization of a magneto-rheological rotary brake in a prosthetic knee

    Science.gov (United States)

    Gudmundsson, K. H.; Jonsdottir, F.; Thorsteinsson, F.

    2010-03-01

    Magneto-rheological (MR) fluids have been successfully introduced to prosthetic devices. One such device is a biomechanical prosthetic knee that uses MR fluids to actively control its rotary stiffness. The brake is rotational, utilizing the MR fluid in shear mode. In this study, the geometrical design of the MR brake is addressed. This includes the design of the magnetic circuit and the geometry of the fluid chamber. Mathematical models are presented that describe the rotary torque of the brake. A novel perfluorinated polyether (PFPE)-based MR fluid is introduced, whose properties are tailored for the prosthetic knee. On-state and off-state rheological measurements of the MR fluid are presented. The finite element method is used to evaluate the magnetic flux density in the MR fluid. The design is formulated as an optimization problem, aiming to maximize the braking torque. A parametric study is carried out for several design parameters. Subsequently, a multi-objective optimization problem is defined that considers three design objectives: the field-induced braking torque, the off-state rotary stiffness and the weight of the brake. Trade-offs between the three design objectives are investigated which provides a basis for informed design decisions on furthering the success of the MR prosthetic knee.

  10. Durability investigation on torque control of a magneto-rheological brake: experimental work

    Science.gov (United States)

    Kim, Wan Ho; Park, Jhin Ha; Kim, Gi-Woo; Shin, Cheol Soo; Choi, Seung-Bok

    2017-03-01

    This study experimentally investigates the torque control durability of a disc brake featuring a magneto-rheological (MR) fluid. An appropriate size of MR disc brake is designed based on a mathematical model, and a prototype is manufactured. A small-scale laboratory-scale test bed is then developed using a DC motor, in-line torque sensor, and the MR brake. S45C and S20C steels are inserted into a tapered hole on the surface of the brake disc. After 105 cycles of operation in shear mode, the wear properties of the MR brake are characterized by average surface roughness measurements, scanning electron microscope images, and energy dispersive x-ray spectra. The torque control performances before and after the operation cycles are examined using open-loop control and closed-loop proportional-integral-derivative control. As expected, the control performance degraded after 105 cycles of operation in the open-loop case, but not in the closed-loop case. This aspect is demonstrated by the sinusoidal torque-tacking control performance before and after the operation cycles.

  11. Design of a 7-DOF haptic master using a magneto-rheological devices for robot surgery

    Science.gov (United States)

    Kang, Seok-Rae; Choi, Seung-Bok; Hwang, Yong-Hoon; Cha, Seung-Woo

    2017-04-01

    This paper presents a 7 degrees-of-freedom (7-DOF) haptic master which is applicable to the robot-assisted minimally invasive surgery (RMIS). By utilizing a controllable magneto-rheological (MR) fluid, the haptic master can provide force information to the surgeon during surgery. The proposed haptic master consists of three degrees motions of X, Y, Z and four degrees motions of the pitch, yaw, roll and grasping. All of them have force feedback capability. The proposed haptic master can generate the repulsive forces or torques by activating MR clutch and MR brake. Both MR clutch and MR brake are designed and manufactured with consideration of the size and output torque which is usable to the robotic surgery. A proportional-integral-derivative (PID) controller is then designed and implemented to achieve torque/force tracking trajectories. It is verified that the proposed haptic master can track well the desired torque and force occurred in the surgical place by controlling the input current applied to MR clutch and brake.

  12. Optimal design of disc-type magneto-rheological brake for mid-sized motorcycle: experimental evaluation

    Science.gov (United States)

    Sohn, Jung Woo; Jeon, Juncheol; Nguyen, Quoc Hung; Choi, Seung-Bok

    2015-08-01

    In this paper, a disc-type magneto-rheological (MR) brake is designed for a mid-sized motorcycle and its performance is experimentally evaluated. The proposed MR brake consists of an outer housing, a rotating disc immersed in MR fluid, and a copper wire coiled around a bobbin to generate a magnetic field. The structural configuration of the MR brake is first presented with consideration of the installation space for the conventional hydraulic brake of a mid-sized motorcycle. The design parameters of the proposed MR brake are optimized to satisfy design requirements such as the braking torque, total mass of the MR brake, and cruising temperature caused by the magnetic-field friction of the MR fluid. In the optimization procedure, the braking torque is calculated based on the Herschel-Bulkley rheological model, which predicts MR fluid behavior well at high shear rate. An optimization tool based on finite element analysis is used to obtain the optimized dimensions of the MR brake. After manufacturing the MR brake, mechanical performances regarding the response time, braking torque and cruising temperature are experimentally evaluated.

  13. Modeling of Magneto-Rheological Damper with Neural Network

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    With the revival of magnetorheological technology research in the 1980's, its application in vehicles is increasingly focused on vibration suppression. Based on the importance of magnetorheological damper modeling, nonparametric modeling with neural network, which is a promising development in semi-active online control of vehicles with MR suspension, has been carried out in this study. A two layer neural network with 7 neurons in a hidden layer and 3 inputs and 1 output was established to simulate the behavior of MR damper at different excitation currents. In the neural network modeling, the damping force is a function of displacement, velocity and the applied current. A MR damper for vehicles is fabricated and tested by MTS; the data acquired are utilized for neural network training and validation. The application and validation show that the predicted forces of the neural network match well with the forces tested with a small variance, which demonstrates the effectiveness and precision of neural network modeling.

  14. Experimental Studies on High-Frequency Performance of the Inverse Control Magneto-Rheological Damper

    Institute of Scientific and Technical Information of China (English)

    DU Xiuli; LIAO Weizhang; NIU Dongxu

    2006-01-01

    Severe vibration of underground structures may be induced under blast loads.According to the characteristics of the explosion-induced ground shock wave,a new-type damper,inverse control magneto-rheological(MR) damper was designed to control the vibration.The high-frequency performance test of the MR damper was carried out on the small shaking table.It is shown that the performance can be modeled by use of the modified Bouc-Wen model,and the pa rameters of the model keep stable in the range of 15-50 Hz.

  15. The role of negative stiffness in semi-active control of magneto-rheological dampers

    DEFF Research Database (Denmark)

    Høgsberg, Jan Becker

    2011-01-01

    The performance of external dampers depends on the particular combination of energy dissipation and stiffness, where in general damping increases with decreasing damper stiffness. It is therefore of great interest to minimize or even introduce negative damper stiffness. The present paper proposes...... adaptive control strategies for the applied voltage of a semi-active magneto-rheological damper. From linear equivalent models obtained by harmonic averaging it is found that these control strategies introduce equivalent negative stiffness, and by numerical simulations it is illustrated that they lead...

  16. A Course in Fluid Mechanics of Suspensions.

    Science.gov (United States)

    Davis, Robert H.

    1989-01-01

    Discusses a course focusing on fluid mechanics and physical chemistry of suspensions. Describes the main themes of the lectures and includes a list of course outlines. Possible textbooks and many journal articles are listed. (YP)

  17. A Course in Fluid Mechanics of Suspensions.

    Science.gov (United States)

    Davis, Robert H.

    1989-01-01

    Discusses a course focusing on fluid mechanics and physical chemistry of suspensions. Describes the main themes of the lectures and includes a list of course outlines. Possible textbooks and many journal articles are listed. (YP)

  18. Design and characterization of a magneto-rheological series elastic actuator for a lower extremity exoskeleton

    Science.gov (United States)

    Chen, Bing; Zhao, Xuan; Ma, Hao; Qin, Ling; Liao, Wei-Hsin

    2017-10-01

    In this paper, an innovative actuator named magneto-rheological series elastic actuator (MRSEA) is designed for the knee joints of a lower extremity exoskeleton CUHK-EXO. MRSEA is designed to reduce the mechanical impedance of the exoskeleton and filter out unwanted collisions. It can also provide large controllable braking torque with low power, and hence improve the system energy efficiency. A description of CUHK-EXO developed to help paraplegic patients regain the mobility to stand up, sit down and walk is firstly introduced, followed by the mechanical design of MRSEA and simulation of the torsion spring pack (TSP) and magneto-rheological (MR) brake of MRSEA. Prototype of MRSEA is fabricated. Preliminary tests are performed to investigate the characteristics of the TSP and MR brake, and walking experiments with a paraplegic patient are performed to evaluate the performance of MRSEA. Experimental results of MRSEA match the modeling and simulation. As compared with the electric motor, the energy efficiency of the innovative MRSEA is improved by 52.8% during a gait cycle.

  19. A microsphere suspension model of metamaterial fluids

    Directory of Open Access Journals (Sweden)

    Qian Duan

    2017-05-01

    Full Text Available Drawing an analogy to the liquid phase of natural materials, we theoretically propose a microsphere suspension model to realize a metamaterial fluid with artificial electromagnetic indexes. By immersing high-ε, micrometer-sized dielectric spheres in a low-ε insulating oil, the structured fluid exhibits liquid-like properties from dispersing phase as well as the isotropic negative electromagnetic parameters caused by Mie resonances from dispersed microspheres. The work presented here will benefit the development of structured fluids toward metamaterials.

  20. An Analytical Study of Fire Out of Battery Using Magneto Rheological Dampers

    Directory of Open Access Journals (Sweden)

    Mehdi Ahmadian

    2002-01-01

    Full Text Available The application of magneto rheological dampers for controlling the dynamics of a fire out-of-battery recoil system is examined, using a dynamic simulation of a 105mm cannon. Upon providing a brief background on MR dampers and fire out-of-battery dynamics, we will describe the simulation model, along with some of the results obtained from the model. The simulation results show that although conventional hydraulic recoil dampers can be designed and tuned to control fire out-of-battery dynamics as effectively as MR dampers, they are not able to perform well when firing faults are encountered. The results show that MR dampers are able to adapt to the firing faults such as pre-fire, hang-fire, and misfire and provide "soft recoil" under all firing conditions. The inability of conventional hydraulic dampers to adapt to the firing faults can yield recoil dynamics that seriously jeopardize the performance of the gun. Therefore, the results presented here show that MR dampers may provide an enabling technology in achieving fire out-of-battery under all firing conditions.

  1. Bifurcations and chaos of a vibration isolation system with magneto-rheological damper

    Directory of Open Access Journals (Sweden)

    Hailong Zhang

    2016-03-01

    Full Text Available Magneto-rheological (MR damper possesses inherent hysteretic characteristics. We investigate the resulting nonlinear behaviors of a two degree-of-freedom (2-DoF MR vibration isolation system under harmonic external excitation. A MR damper is identified by employing the modified Bouc-wen hysteresis model. By numerical simulation, we characterize the nonlinear dynamic evolution of period-doubling, saddle node bifurcating and inverse period-doubling using bifurcation diagrams of variations in frequency with a fixed amplitude of the harmonic excitation. The strength of chaos is determined by the Lyapunov exponent (LE spectrum. Semi-physical experiment on the 2-DoF MR vibration isolation system is proposed. We trace the time history and phase trajectory under certain values of frequency of the harmonic excitation to verify the nonlinear dynamical evolution of period-doubling bifurcations to chaos. The largest LEs computed with the experimental data are also presented, confirming the chaotic motion in the experiment. We validate the chaotic motion caused by the hysteresis of the MR damper, and show the transitions between distinct regimes of stable motion and chaotic motion of the 2-DoF MR vibration isolation system for variations in frequency of external excitation.

  2. Bifurcations and chaos of a vibration isolation system with magneto-rheological damper

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Hailong [Magneto-electronics Lab, School of Physics and Technology, Nanjing Normal University, Nanjing 210046 (China); Vibration Control Lab, School of Electrical and Automation Engineering, Nanjing Normal University, Nanjing 210042 (China); Zhang, Ning [Magneto-electronics Lab, School of Physics and Technology, Nanjing Normal University, Nanjing 210046 (China); Min, Fuhong; Yan, Wei; Wang, Enrong, E-mail: erwang@njnu.edu.cn [Vibration Control Lab, School of Electrical and Automation Engineering, Nanjing Normal University, Nanjing 210042 (China)

    2016-03-15

    Magneto-rheological (MR) damper possesses inherent hysteretic characteristics. We investigate the resulting nonlinear behaviors of a two degree-of-freedom (2-DoF) MR vibration isolation system under harmonic external excitation. A MR damper is identified by employing the modified Bouc-wen hysteresis model. By numerical simulation, we characterize the nonlinear dynamic evolution of period-doubling, saddle node bifurcating and inverse period-doubling using bifurcation diagrams of variations in frequency with a fixed amplitude of the harmonic excitation. The strength of chaos is determined by the Lyapunov exponent (LE) spectrum. Semi-physical experiment on the 2-DoF MR vibration isolation system is proposed. We trace the time history and phase trajectory under certain values of frequency of the harmonic excitation to verify the nonlinear dynamical evolution of period-doubling bifurcations to chaos. The largest LEs computed with the experimental data are also presented, confirming the chaotic motion in the experiment. We validate the chaotic motion caused by the hysteresis of the MR damper, and show the transitions between distinct regimes of stable motion and chaotic motion of the 2-DoF MR vibration isolation system for variations in frequency of external excitation.

  3. An Evaluation of Magneto Rheological Dampers for Controlling Gun Recoil Dynamics

    Directory of Open Access Journals (Sweden)

    Mehdi Ahmadian

    2001-01-01

    Full Text Available The application of magneto rheological dampers for controlling recoil dynamics is examined, using a recoil demonstrator that includes a single-shot 50 caliber BMG rifle action and a MR damper. The demonstrator is selected such that it can adequately represent the velocities that commonly occur in weapons with a recoil system, and can be used for collecting data for analyzing the effects of MR dampers on recoil dynamics. The MR damper is designed so that it can work effectively at the large velocities commonly occurring in gun recoil, and also be easily adjusted to reasonably optimize the damper performance for the recoil demonstrator. The test results show that it is indeed possible to design and use MR dampers for recoil applications, which subject the damper to relative velocities far larger than the applications that such dampers have commonly been used for (i.e., vehicle applications. Further, the results indicate that the recoil force increases and the recoil stroke decreases nonlinearly with an increase in the damping force. Also of significance is the fact that the adjustability of MR dampers can be used in a closed-loop system such that the large recoil forces that commonly occur upon firing the gun are avoided and, simultaneously, the recoil stroke is reduced. This study points to the need for several areas of research including establishing the performance capabilities for MR dampers for gun recoil applications in an exact manner, and the potential use of such dampers for a fire out of battery recoil system.

  4. Magneto-rheological response of elastomer composites with hybrid-magnetic fillers

    Science.gov (United States)

    Aloui, Sahbi; Klüppel, Manfred

    2015-02-01

    We study the magneto-rheological response of hybrid-magnetic elastomer composites consisting of two different magnetic filler particles at fixed overall concentration. Thereby, we focus on an optimization of mechanical and magnetic properties by combining highly reinforcing magnetic nano-particles (MagSilica) with micro-sized carbonyl-iron particles (CIP), which exhibit high switch ability in a magnetic field. We observe a symbiotic interaction of both filler types, especially in the case when an orientation of the magnetic filler particles is achieved due to curing in an external magnetic field. The orientation effect is significant only for the micro-sized CIP particles with high saturation magnetization, indicating that the induced magnetic moment for the nano-sized particles is too small for delivering sufficient attraction between the particles in an external magnetic field. A pronounced switching behavior is observed for the non-cross-linked melts with 15 and 20 vol.% CIP, whereby the small strain modulus increases by more than 50%. For the sample without the coupling agent silane, one even observes a relative modulus increase of about 140%, which can be related to the combined effect of a higher mobility of the particles without a silane layer and the ability of the particles to come in close contact when they are arranged in strings along the field lines. For the cross-linked samples, a maximum switching effect of about 30% is achieved for the system with pure CIP. This magneto-sensitivity decreases successively if CIP is replaced by MagSilica, while the tensile strength of the systems increases significantly. The use of silane reduces the switching effect, but it is necessary for a good mechanical performance by delivering strong chemical bonding of the magnetic filler particles to the polymer matrix.

  5. GENERALIZED ASYMMETRIC HYSTERESIS MODEL OF CONTROLLABLE MAGNETORHEOLOGICAL DAMPER FOR VEHICLE SUSPENSION ATTENUATION

    Institute of Scientific and Technical Information of China (English)

    Wang Enrong; Ma Xiaoqing; Su Chunyi; Rakheja Subhash

    2004-01-01

    A generalized model is synthesized to characterize the asymmetric hysteresis force-velocity (F-v) properties of the magneto-rheological (MR) fluids damper.The model is represented as a function of the command current,excitation frequency,and displacement amplitude,based on the symmetric and asymmetric sigmoid functions.The symmetric hysteresis damping properties of the controllable MR-damper and properties of the conventional passive hydraulic damper can also be described by the proposed model.The validity of the model is verified by experiments,which show that the results calculated from the model are consistent with the measured data.In addition,it is shown that the model applies to a wide vibration frequency range.The proposed model has potential application in vehicle suspension design employing the symmetry MR-damper,and also in developing the asymmetry MR-damper especially for the vehicle suspension attenuation.

  6. Investigation of Mechanical Properties of Magneto-Rheological Ethylene Propylene Diene Monomer and Natural Rubber Type Synthetic Rubbers for Both Isotropic and Anisotropic Situations

    Directory of Open Access Journals (Sweden)

    Uğur Mazlum

    2015-12-01

    Full Text Available Magneto-rheological (MR materials are in a smart material class that has the rheological properties to be quickly and reversibly controlled with the external magnetic field applications. Considering the technological developments the rubber-like smart materials has had a more functional usage area with magneto- rheological effect. This study investigates the axial mechanical properties of magneto-rheological Ethylene Propylene Diene Monomer (EPDM and Natural Rubber (NR type synthetic rubbers for isotropic and anisotropic situations. Also, these composite materials were built by means of hot press systems as either isotropic or anisotropic using magnetic field application after addition of ferromagnetic powders. The influence of magnetic field was investigated. In this study, NR rubber was found to be more susceptible in terms of smart material properties unlike EPDM synthetic rubber.

  7. Application of Magneto Rheological Material and Mechanics in Seismic Mitigation and Isolation in Bridge Engineering%磁流变材料与装置在桥梁工程减隔震中的应用

    Institute of Scientific and Technical Information of China (English)

    宏永锋; 韩丽丽

    2011-01-01

    This thesis investigates the basic characteristics, constituents and producing procedure of Magneto Rheological Fluid (MRF).MRF is a kind of controllable fluid.It is a sort of suspended substances comprised of non-conducting magnetic fluid and tiny soft magnetism granules that is evenly distributed.It exhibits low viscidity Newton fluid on the condition of null-magnetic field.In contrast, it shows characteristics such as the adhesiveness and low fluidity of Bingham in the scale of millisecond.Compared to Electricity Rheological Fluid (ERF), MRF has the advantages such as Field coil voltage is low, shear yield strength is high and it is not sensitive to impurities, temperature and other factors.This give the Magneto Rheological Damping made by it great prospects in bridge structuring, the areas of active, semi-active vibration control in construction structuring.Considering the issue of economy, when applied in bridge structuring, Magneto Rheological Damping are usually used in Cable-stayed bridge cable reducing vibration and some important multi-span continuous bridge with high piers.Also, Magneto Rheological Damping can be used in Simply supported steel truss railway bridge.%介绍了磁流变液基本特性、组成及磁流变液的制备工艺.磁流变液属可控流体,是由非导磁性液体和均匀分散其中的微小软磁性颗粒混合而成的悬浮体.在零磁场条件下呈现出低粘度牛顿流体特性;在强磁场作用下,则可在毫秒级的时间内呈现出高粘度、低流动性的Bingham体特性.与电流变液相比,磁流变液具有励磁线圈工作电压低、剪切屈服强度高、对体内杂质温度等因素不敏感等优点.这使得由其制成的磁流变阻尼器在桥梁结构、建筑结构主动、半主动震动控制领域展现了很好的应用前景.考虑到经济性,目前,桥梁结构用磁流变阻尼器主要针对斜拉桥拉索减振及重要的多跨高墩连续梁桥.铁路简支钢桁梁桥也有应用.

  8. A comparative analysis of passive twin tube and skyhook MRF dampers for motorcycle front suspensions

    Science.gov (United States)

    Ahmadian, Mehdi; Gravatt, John

    2004-07-01

    A comparative analysis between conventional passive twin tube dampers and skyhook-controlled magneto-rheological fluid (MRF) dampers for motorcycle front suspensions is provided, based on single axis testing in a damper test rig and suspension performance testing in road trials. Performance motorcycles, while boasting extremely light suspension components and competition-ready performance, have an inherent weakness in comfort, as the suspension systems are designed primarily for racing purposes. Front suspension acceleration and shock loading transmit directly through the front suspension triple clamp into the rider's arms and shoulders, causing rapid fatigue in shoulder muscles. Magneto-rheological fluid dampers and skyhook control systems offer an alternative to conventional sport motorcycle suspensions - both performance and comfort can be combined in the same package. Prototype MRF dampers designed and manufactured specifically for this application require no more space than conventional twin tube designs while adding only 1.7 pounds total weight to the system. The MRF dampers were designed for high controllability and low power consumption, two vital considerations for a motorcycle application. The tests conducted include the dampers' force-velocity curve testing in a damper test rig and suspension performance based on damper position, velocity, and acceleration measurement. Damper test rig results show the MRF dampers have a far greater range of adjustability than the test vehicle's OEM dampers. Combined with a modified sky-hook control system, the MRF dampers can greatly decrease the acceleration and shock loading transmitted to the rider through the handlebars while contributing performance in manners such as anti-dive under braking. Triple clamp acceleration measurements from a variety of staged road conditions, such as sinusoidal wave inputs, will be compared to subjective test-rider field reports to establish a correlation between rider fatigue and the

  9. Effects of the lower extremities muscle activation during muscular strength training on an unstable platform with magneto-rheological dampers

    Science.gov (United States)

    Piao, YongJun; Choi, YounJung; Kim, JungJa; Kwan, TaeKyu; Kim, Nam-Gyun

    2009-03-01

    Adequate postural balance depends on the spatial and temporal integration of vestibular, visual, and somatosensory information. Especially, the musculoskeletal function (range of joint, flexibility of spine, muscular strength) is essential in maintaining the postural balance. Muscular strength training methods include the use of commercialized devices and repeatable resistance training tools (rubber band, ball, etc). These training systems cost high price and can't control of intensity. Thus we suggest a new training system which can adjust training intensity and indicate the center of pressure of a subject while the training was passively controlled by applying controlled electric current to the Magneto- Rheological damper. And we performed experimental studies on the muscular activities in the lower extremities during maintaining, moving and pushing exercises on an unstable platform with Magneto rheological dampers. A subject executed the maintaining, moving and pushing exercises which were displayed in a monitor. The electromyographic signals of the eight muscles in lower extremities were recorded and analyzed in the time and frequency domain: the muscles of interest were rectus femoris, biceps femoris, tensor fasciae latae, vastus lateralis, vastus medialis, gastrocnemius, tibialis anterior, and soleus. The experimental results showed the difference of muscular activities at the four moving exercises and the nine maintaining exercises. The rate of the increase in the muscular activities was affected by the condition of the unstable platform with MR dampers for the maintaining and moving exercises. The experimental results suggested the choice of different maintaining and moving exercises could selectively train different muscles with varying intensity. Furthermore, the findings also suggested the training using this system can improve the ability of postural balance.

  10. One-fluid description of turbulently flowing suspension

    OpenAIRE

    L'vov, Victor S.; Pomyalov, Anna

    2002-01-01

    We suggested a one-fluid model of a turbulent dilute suspension which accounts for the ``two-way'' fluid-particle interactions by $k$-dependent effective density of suspension and additional damping term in the Navier-Stokes equation. We presented analytical description of the particle modification of turbulence including scale invariant suppression of a small $k$ part of turbulent spectrum (independent of the particle response time) and possible enhancemenent of large $k$ region [up to the f...

  11. Method of hardening a fluid mass

    NARCIS (Netherlands)

    Zitha, P.L.J.; Jansen, J.D.

    2003-01-01

    The invention relates to a method of hardening a fluid mass in contact with a wall, in a desirable shape. According to the invention, the fluid mass is a magneto-rheological fluid mixture that in addition to at least one hardening component comprises a particulate magnetic component, with minimally

  12. Method of hardening a fluid mass

    NARCIS (Netherlands)

    Zitha, P.L.J.; Jansen, J.D.

    2003-01-01

    The invention relates to a method of hardening a fluid mass in contact with a wall, in a desirable shape. According to the invention, the fluid mass is a magneto-rheological fluid mixture that in addition to at least one hardening component comprises a particulate magnetic component, with minimally

  13. Analysis and suppression of hysteresis effect in semi-actively controlled MR-suspension

    Institute of Scientific and Technical Information of China (English)

    LU Feng-xia; WANG En-rong; YING Liang

    2007-01-01

    Magneto-rheological (MR) fluid-based dampers are currently being explored for their potential implementation in intelligent vehicle suspension designs. Due to inherent hysteretic force properties of the MR dampers, analyzing and suppressing the MR-damper hysteresis effects, therefore, impose a great challenge. A quarter-vehicle MR-suspension model is formulated in conjunction with proposed hysteretic and mean MR-damper models, and the passive and semi-actively controlled MR-suspension systems are focused to investigate the influence of MR-damper force hysteresis. The semi-actively controlled MR-suspension employs the "on-off"control law in response to direction of the damper velocity, so as to generate the asymmetric damping force property form the symmetric MR-damper design. The results show that the MR-damping hysteresis yields serious transients and oscillations in responses for the semi-actively controlled MR-suspension than the passive MR-suspension due to the current-switching discontinuity, and would thus deteriorate the suspension performance. The undesired strong transients and oscillations in responses can be effectively suppressed by employing the proposed smooth technique without phase shift for modulating the command current discontinuity.

  14. VELOCITY AND SUSPENSION CONCENTRATION IN SEDIMENT-MIXED FLUID

    Institute of Scientific and Technical Information of China (English)

    B.S.MAZUMDER; K.GHOSHAL

    2002-01-01

    The present paper is focussed on the effects of viscous and turbulent shear stresses on both vertical velocity and concentration distributions in large suspension of sands. When the flow carries large amount of sediments in suspension,the properties of fluid mixture are changed in terms of modified viscosity,density and fall velocity,and hence the flow characteristics. Theoretical models have been developed for both velocity and concentration profiles,taking into account the viscous and turbulent shear stresses,which are the function of volumetric concentration. Comparison of theoretical models with experimental data reveals that (i) the modified velocity and concentration profiles agree well with the observed data for high suspension,(ii) the higher the sediment suspension,the smaller the vonKarman constant,and (iii) sediment diffusion coefficient is less than momentum diffusion coefficient for fine sands in suspension.

  15. Semi-active control of automotive suspension systems with magnetorheological dampers

    Science.gov (United States)

    Lam, Hiu Fung; Liao, Wei-Hsin

    2001-08-01

    Vibration in today's increasingly high-speed vehicles including automobiles severely affects their ride comfort and safety. The objective of this paper is to develop and study automotive suspension systems with magneto-rheological (MR) fluid dampers for vibration control in order to improve the passenger's comfort and safety. A two degree-of-freedom quarter car model is considered. A mathematical model of MR fluid damper is adopted. In this study, a sliding mode controller is developed by considering loading uncertainty to result in a robust control system. Two kinds of excitations are inputted in order to investigate the performance of the suspension system. The vibration responses are evaluated in both time and frequency domains. Compared to the passive system, the acceleration of the sprung mass is significantly reduced for the system with a controlled MR damper. Under random excitation, the ability of the MR fluid damper to reduce both peak response and root-mean-square response is also shown. The effectiveness of the MR suspension system is also demonstrated via hardware-in-the-loop simulation. The results of this study can be used to develop guidelines to effectively integrate automotive suspensions with MR dampers.

  16. On the influence of the hydrodynamic interactions on the aggregation rate of magnetic spheres in a dilute suspension

    Energy Technology Data Exchange (ETDEWEB)

    Cunha, F.R., E-mail: frcunha@unb.b [Universidade de Brasilia, Faculdade de Tecnologia, Depto. de Engenharia Mecanica, Grupo de Mecanica dos Fluidos de Escoamentos Complexos - VORTEX, Campus Universitario Darcy Ribeiro, 70910-900, Brasilia, DF (Brazil); Couto, H.L.G. [Universidade de Brasilia, Faculdade de Tecnologia, Depto. de Engenharia Mecanica, Grupo de Mecanica dos Fluidos de Escoamentos Complexos - VORTEX, Campus Universitario Darcy Ribeiro, 70910-900, Brasilia, DF (Brazil)

    2011-01-15

    Magnetostatic attraction may lead to formation of aggregates in stable colloidal magnetic suspensions and magneto-rheological suspensions. The aggregation problem of magnetic composites under differential sedimentation is a key problem in the control of the instability of non-Brownian suspensions. Against these attractive forces are the electrostatic repulsion and the hydrodynamic interactions acting as stabilizing effects to the suspension. This work concerns an investigation of the pairwise interaction of magnetic particles in a dilute sedimenting suspension. We focus attention on suspensions where the Peclet number is large (negligible Brownian motion) and where the Reynolds number (negligible inertia) is small. The suspension is composed of magnetic micro-spheres of different radius and density immersed in a Newtonian fluid moving under the action of gravity. The theoretical calculations are based on direct computations of the hydrodynamic and the magnetic interactions among the rigid spheres in the regime of low particle Reynolds number. From the limiting trajectory in which aggregation occurs, we calculate the collision efficiency, representing the dimensionless rate at which aggregates are formed. The numerical results show clear evidence that the hydrodynamic interactions are of fundamental relevance in the process of magnetic particle aggregation. We compare the stabilizing effects between electrostatic repulsion and hydrodynamic interactions.

  17. A comparison of 200 kN magneto-rheological damper models for use in real-time hybrid simulation pretesting

    Science.gov (United States)

    Jiang, Z.; Christenson, R.

    2011-06-01

    Control devices can be used to dissipate the energy of a civil structure subjected to dynamic loading, such as earthquake, wave and wind excitation, thus reducing structural damage and preventing failure. The magneto-rheological (MR) fluid damper is a promising device for use in civil structures due to its mechanical simplicity, inherent stability, high dynamic range, large temperature operating range, robust performance, and low power requirements. The MR damper is intrinsically nonlinear and rate dependent. Thus a challenging aspect of applying this technology is the development of accurate models to describe the behavior of such dampers for control design and evaluation purposes. In particular, a new type of experimental testing called real-time hybrid simulation (RTHS) combines numerical simulation with laboratory testing of physical components. As with any laboratory testing, safety is of critical importance. For RTHS in particular the feedback and dynamic interaction of physical and numerical components can result in potentially unstable behavior. For safety purposes, it is desired to conduct pretest simulations where the physical specimen is replaced with an appropriate numerical model yet the numerical RTHS component is left unchanged. These pretest simulations require a MR damper model that can exhibit stability and convergence at larger fixed integration time steps, and provide computational efficiency, speed of calculation, and accuracy during pretest verification of the experimental setup. Several models for MR dampers have been proposed, including the hyperbolic tangent, Bouc-Wen, viscous plus Dahl and algebraic models. This paper examines the relative performance of four MR damper models of large-scale 200 kN MR dampers as needed for pretest simulations of RTHS. Experimental tests are conducted on two large-scale MR dampers located at two RTHS test facilities at the Smart Structures Technology Laboratory at the University of Illinois at Urbana

  18. Stochastic micro-vibration suppression of a sandwich plate using a magneto-rheological visco-elastomer core

    Science.gov (United States)

    Ying, Z. G.; Ni, Y. Q.; Ye, S. Q.

    2014-02-01

    Magneto-rheological visco-elastomer (MRVE) is used to construct sandwich plates for micro-vibration control. The micro-vibration response of a sandwich plate with an MRVE core under stochastic support motion excitation is studied to evaluate the vibration suppression capability. The dynamic behavior of MRVE in micro-vibration is characterized by a non-homogeneous complex modulus dependent on the vibration frequency and controllable by an applied magnetic field, in which the effect of the localized magnetic field distribution is considered. The partial differential equations for the coupled transverse and longitudinal motions of the sandwich plate are derived from the dynamic equilibrium, constitutive and geometric relations. A frequency-domain solution method for the stochastic micro-vibration response of sandwich plates is developed based on the Galerkin method and random vibration theory. The partial differential equations are first converted into ordinary differential equations according to the Galerkin method. Then the expressions for the frequency-response function, response power spectral density and root-mean-square velocity spectrum in terms of the one-third octave frequency band for micro-vibration are obtained. Finally, numerical results are given to illustrate the high response reduction capacity of the MRVE sandwich plate under stochastic support motion excitation, and the influence of the MRVE parameters and localized magnetic field placement on the micro-vibration response.

  19. Fluid Velocity Fluctuations in a Suspension of Swimming Protists

    CERN Document Server

    Rushkin, Ilia; Goldstein, Raymond E

    2010-01-01

    In dilute suspensions of swimming microorganisms the local fluid velocity is a random superposition of the flow fields set up by the individual organisms, which in turn have multipole contributions decaying as inverse powers of distance from the organism. Here we show that the conditions under which the central limit theorem guarantees a Gaussian probability distribution function of velocities are satisfied when the leading force singularity is a Stokeslet, but are not when it is any higher multipole. These results are confirmed by numerical studies and by experiments on suspensions of the alga Volvox carteri, which show that deviations from Gaussianity arise from near-field effects.

  20. Magnetic fluids - suspensions of magnetic dipoles and their magnetic control

    CERN Document Server

    Odenbach, S

    2003-01-01

    Suspensions of magnetic nanoparticles exhibit normal liquid behaviour coupled with superparamagnetic properties. This leads to the possibility to control the properties and the flow of these liquids with moderate magnetic fields. The magnetic control enables various experiments in fluid mechanics and gives rise to the development of numerous technical and medical applications. Ferrofluids and their general properties will be introduced and, as examples for the magnetic control of their flow and properties, thermomagnetic convection and magnetoviscous effects will be discussed in some detail.

  1. Decomposition approach to model smart suspension struts

    Science.gov (United States)

    Song, Xubin

    2008-10-01

    Model and simulation study is the starting point for engineering design and development, especially for developing vehicle control systems. This paper presents a methodology to build models for application of smart struts for vehicle suspension control development. The modeling approach is based on decomposition of the testing data. Per the strut functions, the data is dissected according to both control and physical variables. Then the data sets are characterized to represent different aspects of the strut working behaviors. Next different mathematical equations can be built and optimized to best fit the corresponding data sets, respectively. In this way, the model optimization can be facilitated in comparison to a traditional approach to find out a global optimum set of model parameters for a complicated nonlinear model from a series of testing data. Finally, two struts are introduced as examples for this modeling study: magneto-rheological (MR) dampers and compressible fluid (CF) based struts. The model validation shows that this methodology can truly capture macro-behaviors of these struts.

  2. Optimal design and selection of magneto-rheological brake types based on braking torque and mass

    Science.gov (United States)

    Nguyen, Q. H.; Lang, V. T.; Choi, S. B.

    2015-06-01

    In developing magnetorheological brakes (MRBs), it is well known that the braking torque and the mass of the MRBs are important factors that should be considered in the product’s design. This research focuses on the optimal design of different types of MRBs, from which we identify an optimal selection of MRB types, considering braking torque and mass. In the optimization, common types of MRBs such as disc-type, drum-type, hybrid-type, and T-shape types are considered. The optimization problem is to find an optimal MRB structure that can produce the required braking torque while minimizing its mass. After a brief description of the configuration of the MRBs, the MRBs’ braking torque is derived based on the Herschel-Bulkley rheological model of the magnetorheological fluid. Then, the optimal designs of the MRBs are analyzed. The optimization objective is to minimize the mass of the brake while the braking torque is constrained to be greater than a required value. In addition, the power consumption of the MRBs is also considered as a reference parameter in the optimization. A finite element analysis integrated with an optimization tool is used to obtain optimal solutions for the MRBs. Optimal solutions of MRBs with different required braking torque values are obtained based on the proposed optimization procedure. From the results, we discuss the optimal selection of MRB types, considering braking torque and mass.

  3. Viscosity behavior of magnetic suspensions in fluid-assisted finishing

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    Magnetic fluid-assisted finishing has been verified both theoretically and experimentally as an effective fabrication technology for optical mirrors and lenses. The purpose of this paper is to introduce a novel design of polishing tool and demonstrate the possible applications of this technology. The work includes studying the viscosity of the magnetic suspensions of micrometer-sized Carbonyl iron particles under the influence of a magnetic field. Both the cases of magnetizable suspension with and without abrasive cerium oxide particles are studied for their ensuing polishing effectiveness. Determination of material removal function is conducted using a Wyko Nat1100 interferometer. Experiments to reduce surface roughness with the proposed tool are also performed using a K9 mirror as the work-piece. Results show that the surface accuracy is improved over three times to less than 0.5 nm after two cycles of polishing.

  4. DESIGN METHOD OF MAGNETORHEOLOGICAL FLUID SHOCK ABSORBER FOR CAR SUSPENSION

    Institute of Scientific and Technical Information of China (English)

    LIAO Changrong; ZHANG Honghui; YU Miao; CHEN Weimin

    2008-01-01

    The Bingham constitutive model, which is previously used in depiction of magnetorheological (MR) fluids rheological behaviors for design devices, exhibits discontinuous characteristics in representation of pre-yield behaviors and post-yield behaviors. A Biviscous constitutive model is presented to depict rheological behaviors of MR fluids and design automotive shock absorber. Quasi-static flow equations of MR fluids in annular channels are set theoretically up based on Navier-Stokes equations and several rational simplifications are made. And both flow boundary conditions and flow compatibilities conditions are established. Meantime, analytical velocity profiles of MR fluids though annular channels are obtained via solution of the quasi-static flow equations using Biviscous constitutive model. The prediction methodology of damping force offered by MR fluid shock absorber is formulated and damping performances are predicated in order to determine design parameters. MR fluid shock absorber for Mazda 323 car suspension is designed and fabricated in Chongqing University, China. Measurements from sinusoidal displacement cycle by Shanchuan Shock Absorber Ltd. of China North Industry Corporation reveal that the analytical methodology and design theory are reasonable.

  5. 汽车动力总成磁流变悬置的磁路模拟分析与试验验证%Magnetic Circuit Simulation and Experimental Verification of A Magneto-rheological (MR) Mount for Automobile Powertrain

    Institute of Scientific and Technical Information of China (English)

    袁杰; 李俊; 苏思超; 付元磊

    2012-01-01

    根据磁流变液的流变特性设计了一种新型半主动磁流变悬置结构,并简述了该悬置结构和工作原理.利用ANSYS电磁场分析模块对悬置结构内部磁场进行了有限元分析,研究了相同磁流变液悬置结构下,不同隔板材料对磁流变液悬置磁场分布的影响,并分别测试了采用不同隔板材料时磁流变液悬置的动特性.结果表明,所选择的低磁导率铝合金隔板材料可改善悬置性能:在磁流变悬置的设计过程中引入ANSYS的电磁场分析方法可行并具有一定的通用性.%According to the special properties of Magnetorheological Fluids (MRF), a new semi-active structure of magneto-rheological (MR) mount is designed, structure and operating principle of this mount is outlined in the paper. FEA is made to the internal magnetic field of the mount using ANSYS electromagnetic field analysis module, which studies the effect of different baffle plate material on distribution of magnetic field of MR mount under the same MR mount structure, dynamic characteristic of the MR mount is tested with different baffle plate material. The results show that the low permeability aluminum alloy baffle plate material can improve performance of the mount; introduction of ANSYS electromagnetic field analysis method in designing MR mount has commonality.

  6. A minimax stochastic optimal semi-active control strategy for uncertain quasi-integrable Hamiltonian systems using magneto-rheological dampers

    DEFF Research Database (Denmark)

    Feng, Ju; Ying, Zu-Guang; Zhu, Wei-Qiu

    2012-01-01

    A minimax stochastic optimal semi-active control strategy for stochastically excited quasi-integrable Hamiltonian systems with parametric uncertainty by using magneto-rheological (MR) dampers is proposed. Firstly, the control problem is formulated as an n-degree-of-freedom (DOF) controlled......, uncertain quasi-integrable Hamiltonian system and the control forces produced by MR dampers are split into the passive part and the semi-active part. Then the passive part is incorporated into the uncontrolled system. After that, the stochastic optimal semi-active control problem is solved by applying...... the minimax stochastic optimal control strategy based on the stochastic averaging method and stochastic differential game. The worst-case disturbances and the optimal controls are obtained by the minimax dynamical programming equation with the constraints of disturbance bounds and MR damper dynamics. Finally...

  7. Control of an Automotive Semi-Active Suspension

    Directory of Open Access Journals (Sweden)

    Jorge de Jesús Lozoya-Santos

    2012-01-01

    Full Text Available Two controllers for an automotive suspensions with Magneto-Rheological (MR dampers are proposed. One is a model-based using the Linear Parameter Varying (LPV approach, and the other is a model-free controller with a Frequency Estimation Based (FEB principle. The LPV controller includes an experimental nonlinear model of an MR damper using only one scheduling parameter. A comparison with a several semiactive controllers for comfort and road holding is discussed. The FEB controller is the best option based on frequency and time response analysis for comfort (10–20%, suspension deflection (30–50%, and road holding (1–5%.

  8. The helicopter dynamic stability analysis in hover condition using magneto-rheological dampers%悬停状态带磁流变减摆器直升机的动稳定性分析

    Institute of Scientific and Technical Information of China (English)

    卫丽君; 李书

    2012-01-01

    Magneto-rheological damper model suitable for helicopter air resonance and momentum theory model of hover condition involving momentum theory were built in this paper. The equations of the two models with the dynamic equations of helicopter rotor/body coupling were solved by Simulink time domain simulation method to obtain the helicopter dynamic stability influenced by Magneto-rheological damper and compared the blade flapping and lagging impacted by Magneto-rheological dampers under different voltages. It could be conclude that under a certain voltage, Magneto-rheological damper was not influenced by duel-frequent excitation, and was good at restraining the helicopter air resonance.%建立了适用于直升机悬停状态动稳定性的磁流变减摆器模型,悬停状态下动力入流模型采用动量理论模型,与直升机旋翼/机体耦合动力学方程组联立,采用Simulink时域仿真的方法计算得到磁流变减摆器对悬停状态下直升机动稳定的影响,对比了不同电压下磁流变减摆器对桨叶挥舞摆振运动的影响.结果表明:对于磁流变减摆器,施加不同电压可得到不同的阻尼力,该性质可以抑制直升机悬停状态动不稳定性.

  9. Near-field magnetostatics and Néel-Brownian interactions mediated magneto-rheological characteristics of highly stable nano-ferrocolloids.

    Science.gov (United States)

    Katiyar, Ajay; Dhar, Purbarun; Das, Sarit K; Nandi, Tandra

    2015-02-28

    Magnetic nanocolloids consisting of synthesized superparamagnetic iron(II,III) oxide nanoparticles (SPION) (5-15 nm) dispersed in poly(ethylene glycol) (PEG) and a nano-silica complex have been synthesized. The PEG-nano-silica complex physically encapsulates the SPIONs, ensuring that there is no phase separation under high magnetic fields (∼1.2 T). Exhaustive magneto-rheological investigations have been performed to understand the structural behavior and response of the ferrocolloids. Remarkable stability and reversibility have been observed under magnetic field for concentrated systems. The results show the impact of particle concentration, size and encapsulation efficiency on parameters such as shear viscosity, yield stress, viscoelastic moduli, magneto-viscous hysteresis, and so on. Analytical models to reveal the system mechanism and mathematically predict the magneto-viscosity and magneto-yield stress have been developed. The mechanistic approach based on near-field magnetostatics and Néel-Brownian interactivities could predict the colloidal properties under the effect of the magnetic field accurately. The colloid exhibits amplified storage and loss moduli together with a highly augmented linear viscoelastic region under magnetic stimuli. The transition of the colloidal state from the fluidic phase to the soft condensed phase and its viscoelastic stimuli under the influence of a magnetic field has been explained based on the mathematical analysis. The remarkable stability, magnetic properties and accurate physical models reveal promise for the colloids in transient situations, namely, magneto-microelectromechanical/nanoelectromechanical devices, anti-seismic damping, biomedical invasive treatments, and so on.

  10. Fluid particle diffusion in a semidilute suspension of model micro-organisms.

    Science.gov (United States)

    Ishikawa, Takuji; Locsei, J T; Pedley, T J

    2010-08-01

    We calculate non-Brownian fluid particle diffusion in a semidilute suspension of swimming micro-organisms. Each micro-organism is modeled as a spherical squirmer, and their motions in an infinite suspension otherwise at rest are computed by the Stokesian-dynamics method. In calculating the fluid particle motions, we propose a numerical method based on a combination of the boundary element technique and Stokesian dynamics. We present details of the numerical method and examine its accuracy. The limitation of semidiluteness is required to ensure accuracy of the fluid particle velocity calculation. In the case of a suspension of non-bottom-heavy squirmers the spreading of fluid particles becomes diffusive in a shorter time than that of the squirmers, and the diffusivity of fluid particles is smaller than that of squirmers. It is confirmed that the probability density distribution of fluid particles also shows diffusive properties. The effect of tracer particle size is investigated by inserting some inert spheres of the same radius as the squirmers, instead of fluid particles, into the suspension. The diffusivity for inert spheres is not less than one tenth of that for fluid particles, even though the particle size is totally different. Scaling analysis indicates that the diffusivity of fluid particles and inert spheres becomes proportional to the volume fraction of squirmers in the semidilute regime provided that there is no more than a small recirculation region around a squirmer, which is confirmed numerically. In the case of a suspension of bottom-heavy squirmers, horizontal diffusivity decreases considerably even with small values of the bottom heaviness, which indicates the importance of bottom heaviness in the diffusion phenomena. We believe that these fundamental findings will enhance our understanding of the basic mechanics of a suspension of swimming micro-organisms.

  11. Free surface flow of a suspension of rigid particles in a non-Newtonian fluid

    DEFF Research Database (Denmark)

    Svec, Oldrich; Skocek, Jan; Stang, Henrik

    2012-01-01

    A numerical framework capable of predicting the free surface flow of a suspension of rigid particles in a non-Newtonian fluid is described. The framework is a combination of the lattice Boltzmann method for fluid flow, the mass tracking algorithm for free surface representation, the immersed...

  12. 基于宾汉模型的磁流变液联轴器工作转矩预测%Transmission torque predicting of magneto-rheological coupler based on Bingham model

    Institute of Scientific and Technical Information of China (English)

    鲁光涛; 李友荣; 王志刚; 宋钢兵

    2015-01-01

    This paper studies the transmission torque characteristics of a rotary drum magneto-rheological coupler. Based on the Bingham model of magneto-rheological damper, a new Bingham model for predicting the transmission torque of magneto-rheological coupler is proposed, and in this new model, the rotational speed ratio of the inner and outer drum of the coupler is used as the input parameter. In this paper, the exponential model is used to compute the Coulomb damping torque and the experimental results indicate that, when the coil current remains constant, the curves between the transmission torque and rotational speed ration are nearly the same as the load increases and decreases, and there is no hysteresis in the curves. For speed ratio of less than 1.3, the torque increases greatly, and for speed ratio of higher than 1.3, it increases much slowly. The proposed Bingham model can correctly predict the transmission torque of magneto-rheological coupler.%针对一种旋转圆筒式磁流变液联轴器,提出了用于预测磁流变液联轴器工作转矩的修正宾汉模型.在该宾汉模型中采用磁流变液联轴器主动转筒和从动转筒之间的转速比 n 作为宾汉模型的输入参数,并采用指数模型描述磁致库仑阻尼力矩.实验结果表明,当线圈电流恒定时,在负载由小-大-小变化过程中,不同初始转速下的转矩-转速比曲线基本重合,且在负载正向增大和反向减小过程中,磁流变液联轴器工作转矩变化曲线基本重合,未形成滞环.当转速比较小(n1.3),工作转矩随负载增大增速减缓,其变化曲线斜率均为0.05,整个转矩-转速比变化曲线与磁流变液联轴器宾汉模型完全吻合,利用磁流变液联轴器力矩宾汉模型可以预测和确定其工作转矩.

  13. Physical therapy applications of MR fluids and intelligent control

    Science.gov (United States)

    Dong, Shufang; Lu, Ke-Qian; Sun, J. Q.; Rudolph, Katherine

    2005-05-01

    Resistance exercise has been widely reported to have positive rehabilitation effects for patients with neuromuscular and orthopaedic conditions. This paper presents an optimal design of magneto-rheological fluid dampers for variable resistance exercise devices. Adaptive controls for regulating the resistive force or torque of the device as well as the joint motion are presented. The device provides both isometric and isokinetic strength training for various human joints.

  14. The Development of Electrorheological Fluids for AN Automotive Semi-Active Suspension System

    Science.gov (United States)

    Weyenberg, Thomas R.; Pialet, Joseph W.; Petek, Nicholas K.

    The feasibility of electrorheological (ER) dampers for an automotive semi-active suspension was evaluated in a three phase program. In the first phase, ER fluid performance targets were derived. The desired ride and handling attributes of the suspension system were translated into damper specifications, which were then translated into the ER fluid performance targets. The damper specifications included dynamic range, bandwidth, power draw, and packaging. The ER fluid performance parameters then included zero-field viscosity, ER stress, response time, and power density. In the second phase, the dampers and the ER fluid were developed to meet the performance targets. Trade-offs were made between damper design and fluid formulation to achieve the desired damper dynamic range and power draw. A state-diagram approach using screen test data was used to select candidate ER fluids. In the third phase of the program, a prototype semi-active suspension system using fast, continuously variable ER dampers was installed on a demonstration vehicle. Heave, pitch, and roll motions of the vehicle were controlled by applying voltages independently to the four dampers as determined by a modified sky-hook algorithm. The system was designed to respond in less than 10 ms with an average power requirement less than 40 W for normal road surfaces and handling. Laboratory data from a pressure driven flow screen test and a damper test are presented that document the ER fluid performance specification and selection process. Vehicle performance data are presented that demonstrate the features of ER technology for the semi-active suspension application. Remaining issues for commercialization of ER fluids are discussed.

  15. Modeling and Optimization of Vehicle Suspension Employing a Nonlinear Fluid Inerter

    Directory of Open Access Journals (Sweden)

    Yujie Shen

    2016-01-01

    Full Text Available An ideal inerter has been applied to various vibration engineering fields because of its superior vibration isolation performance. This paper proposes a new type of fluid inerter and analyzes the nonlinearities including friction and nonlinear damping force caused by the viscosity of fluid. The nonlinear model of fluid inerter is demonstrated by the experiments analysis. Furthermore, the full-car dynamic model involving the nonlinear fluid inerter is established. It has been detected that the performance of the vehicle suspension may be influenced by the nonlinearities of inerter. So, parameters of the suspension system including the spring stiffness and the damping coefficient are optimized by means of QGA (quantum genetic algorithm, which combines the genetic algorithm and quantum computing. Results indicate that, compared with the original nonlinear suspension system, the RMS (root-mean-square of vertical body acceleration of optimized suspension has decreased by 9.0%, the RMS of pitch angular acceleration has decreased by 19.9%, and the RMS of roll angular acceleration has decreased by 9.6%.

  16. Free surface flow of a suspension of rigid particles in a non-Newtonian fluid

    DEFF Research Database (Denmark)

    Svec, Oldrich; Skocek, Jan; Stang, Henrik

    2012-01-01

    efficient, allowing simulations of tens of thousands of rigid particles within a reasonable computational time. Furthermore, the framework does not require any fitting constants or parameters devoid of a clear physical meaning and it is stable, robust and can be easily generalized to a variety of problems......A numerical framework capable of predicting the free surface flow of a suspension of rigid particles in a non-Newtonian fluid is described. The framework is a combination of the lattice Boltzmann method for fluid flow, the mass tracking algorithm for free surface representation, the immersed...... boundary method for two-way coupled interactions between fluid and rigid particles and an algorithm for the dynamics and mutual interactions of rigid particles. The framework is able to simulate the flow of suspensions at the level of the largest suspended particles and, at the same time, the model is very...

  17. Geometry-induced Casimir suspension of oblate bodies in fluids.

    Science.gov (United States)

    Rodriguez, Alejandro W; Reid, M T Homer; Intravaia, Francesco; Woolf, Alexander; Dalvit, Diego A R; Capasso, Federico; Johnson, Steven G

    2013-11-01

    We predict that a low-permittivity oblate body (disk-shaped object) above a thin metal substrate (plate with a hole) immersed in a fluid of intermediate permittivity will experience a metastable equilibrium (restoring force) near the center of the hole. Stability is the result of a geometry-induced transition in the sign of the force, from repulsive to attractive, that occurs as the disk approaches the hole--in planar or nearly planar geometries, the same material combination yields a repulsive force at all separations, in accordance with the Dzyaloshinskiĭ-Lifshitz-Pitaevskiĭ condition of fluid-induced repulsion between planar bodies. We explore the stability of the system with respect to rotations and lateral translations of the disks and demonstrate interesting transitions (bifurcations) in the rotational stability of the disks as a function of their size. Finally, we consider the reciprocal situation in which the disk-plate materials are interchanged and find that in this case the system also exhibits metastability. The forces in the system are sufficiently large to be observed in experiments and should enable measurements based on the diffusion dynamics of the suspended bodies.

  18. Fundamental connections between models of active suspensions and transversely-isotropic fluids

    CERN Document Server

    Holloway, Craig R; Smith, David J; Green, J Edward F; Clarke, Richard J; Dyson, Rosemary J

    2016-01-01

    Suspensions of self-motile, elongated particles are a topic of significant current interest, exemplifying a form of `active matter'. Examples include self-propelling bacteria, algae and sperm, and artificial swimmers. Ericksen's model of a transversely-isotropic fluid [J. L. Ericksen, Colloid Polym. Sci. 173(2):117-122 (1960)] treats suspensions of non-motile particles as a continuum with an evolving preferred direction; this model describes fibrous materials as diverse as extracellular matrix, textile tufts and cellulose microfibres. Director-dependent effects are incorporated through a modified stress tensor with four viscosity-like parameters. By making fundamental connections with recent models for active suspensions, we establish how these viscosity-like parameters relate to the solvent viscosity, volume fraction of particles and their aspect ratio. This comparison reveals previously neglected components of the stress tensor that significantly alter the rheology; these components should be included in mo...

  19. A semi-active control suspension system for railway vehicles with magnetorheological fluid dampers

    Science.gov (United States)

    Wei, Xiukun; Zhu, Ming; Jia, Limin

    2016-07-01

    The high-speed train has achieved great progress in the last decades. It is one of the most important modes of transportation between cities. With the rapid development of the high-speed train, its safety issue is paid much more attention than ever before. To improve the stability of the vehicle with high speed, extra dampers (i.e. anti-hunting damper) are used in the traditional bogies with passive suspension system. However, the curving performance of the vehicle is undermined due to the extra lateral force generated by the dampers. The active suspension systems proposed in the last decades attempt to solve the vehicle steering issue. However, the active suspension systems need extra actuators driven by electrical power or hydraulic power. There are some implementation and even safety issues which are not easy to be overcome. In this paper, an innovative semi-active controlled lateral suspension system for railway vehicles is proposed. Four magnetorheological fluid dampers are fixed to the primary suspension system of each bogie. They are controlled by online controllers for enhancing the running stability on the straight track line on the one hand and further improving the curving performance by controlling the damper force on the other hand. Two control strategies are proposed in the light of the pure rolling concept. The effectiveness of the proposed strategies is demonstrated by SIMPACK and Matlab co-simulation for a full railway vehicle with two conventional bogies.

  20. Delivery of Vegetable Oil Suspensions in a Shear Thinning Fluid for Enhanced Bioremediation

    Energy Technology Data Exchange (ETDEWEB)

    Zhong, Lirong; Truex, Michael J.; Kananizadeh, Negin; Li, Yusong; Lea, Alan S.; Yan, Xiulan

    2015-04-01

    In situ anaerobic biological processes are widely applied for dechlorination of chlorinated solvents in groundwater. A wide range of organic substrates have been tested and applied to support the dechlorination processes. Vegetable oils are a promising substrate and have been shown to induce effective dechlorination, have limited geochemical impacts, and good longevity. Distribution of vegetable oil in the subsurface, because it is a non-aqueous phase material, has typically been addressed by creating emulsified oil solutions. In this study, inexpensive waste vegetable oils were suspended in a xanthan gum solution, a shear-thinning fluid, as an alternative oil delivery mechanism. The stability, oil droplet size and distribution, and rheological behavior of the oil suspensions that are created in the xanthan solutions were studied in batch experiments. The injectability of the suspensions and oil distribution in porous medium were evaluated in column tests. Numerical modeling of the oil droplet transport and distribution in porous media was conducted to help interpret the column-test data. Batch studies showed that simple mixing of vegetable oil and xanthan solution produced stable suspensions of the oil as micron-size droplets. The mixture rheology retains shear-thinning properties that facilitate improved uniformity of substrate distribution in heterogeneous aquifers. Column tests demonstrated successful injection of the vegetable oil suspension into porous medium. This study provided evidence that vegetable oil suspensions in xanthan are a potential substrate to support in situ anaerobic bioremediation with favorable injection properties.

  1. Microgravity Combustion Science and Fluid Physics Experiments and Facilities for the ISS

    Science.gov (United States)

    Lauver, Richard W.; Kohl, Fred J.; Weiland, Karen J.; Zurawski, Robert L.; Hill, Myron E.; Corban, Robert R.

    2001-01-01

    At the NASA Glenn Research Center, the Microgravity Science Program supports both ground-based and flight experiment research in the disciplines of Combustion Science and Fluid Physics. Combustion Science research includes the areas of gas jet diffusion flames, laminar flames, burning of droplets and misting fuels, solids and materials flammability, fire and fire suppressants, turbulent combustion, reaction kinetics, materials synthesis, and other combustion systems. The Fluid Physics discipline includes the areas of complex fluids (colloids, gels, foams, magneto-rheological fluids, non-Newtonian fluids, suspensions, granular materials), dynamics and instabilities (bubble and drop dynamics, magneto/electrohydrodynamics, electrochemical transport, geophysical flows), interfacial phenomena (wetting, capillarity, contact line hydrodynamics), and multiphase flows and phase changes (boiling and condensation, heat transfer, flow instabilities). A specialized International Space Station (ISS) facility that provides sophisticated research capabilities for these disciplines is the Fluids and Combustion Facility (FCF). The FCF consists of the Combustion Integrated Rack (CIR), the Fluids Integrated Rack (FIR) and the Shared Accommodations Rack and is designed to accomplish a large number of science investigations over the life of the ISS. The modular, multiuser facility is designed to optimize the science return within the available resources of on-orbit power, uplink/downlink capacity, crew time, upmass/downmass, volume, etc. A suite of diagnostics capabilities, with emphasis on optical techniques, will be provided to complement the capabilities of the subsystem multiuser or principal investigator-specific experiment modules. The paper will discuss the systems concept, technical capabilities, functionality, and the initial science investigations in each discipline.

  2. Heat transfer with thermal radiation on MHD particle-fluid suspension induced by metachronal wave

    Science.gov (United States)

    Bhatti, M. M.; Zeeshan, A.; Ellahi, R.

    2017-09-01

    In this article, effects of heat transfer on particle-fluid suspension induced by metachronal wave have been examined. The influence of magnetohydrodynamics (MHD) and thermal radiation are also taken into account with the help of Ohm's law and Roseland's approximation. The governing flow problem for Casson fluid model is based on continuity, momentum and thermal energy equation for fluid phase and particle phase. Taking the approximation of long wavelength and zero Reynolds number, the governing equations are simplified. Exact solutions are obtained for the coupled partial differential equations. The impact of all the embedding parameters is discussed with the help of graphs. In particular, velocity profile, pressure rise, temperature profile and trapping phenomena are discussed for all the emerging parameters. It is observed that while fluid parameter enhances the velocity profile, Hartmann number and particle volume fraction oppose the flow.

  3. Heat transfer with thermal radiation on MHD particle–fluid suspension induced by metachronal wave

    Indian Academy of Sciences (India)

    M M BHATTI; A ZEESHAN; R ELLAHI

    2017-09-01

    In this article, effects of heat transfer on particle–fluid suspension induced by metachronal wave have been examined. The influence of magnetohydrodynamics (MHD) and thermal radiation are also taken into account with the help of Ohm’s law and Roseland’s approximation. The governing flow problem for Casson fluid model is based on continuity, momentum and thermal energy equation for fluid phase and particle phase. Taking the approximation of long wavelength and zero Reynolds number, the governing equations are simplified. Exact solutions are obtained for the coupled partial differential equations. The impact of all the embedding parameters is discussed with the help of graphs. In particular, velocity profile, pressure rise, temperature profile and trapping phenomena are discussed for all the emerging parameters. It is observed that while fluid parameter enhances the velocity profile, Hartmann number and particle volume fraction oppose the flow.

  4. Research on Magneto- rheological Fluid Shock Absorption and Shock Control Technology%磁流变液减振器及振动控制技术研究

    Institute of Scientific and Technical Information of China (English)

    郑艳萍; 赵江铭; 刘旭辉; 孟令启

    2007-01-01

    在振动控制领域,用磁流变液减振器对机械设备进行减振防护是近年来的减振技术研究热点之一.阐述了磁流变液减振器的类型及技术特点,对比分析了几种常用的振动控制方法的优异性.讨论了磁流变液减振器的实用价值,指出磁流变液减振器是目前减振设备的开发方向.

  5. Basic Study of Hydraulic System Using Magneto - rheological Fluid%磁流变液介质液压系统的基础研究靠

    Institute of Scientific and Technical Information of China (English)

    赵四海; 方佳雨; 吕兴军

    2005-01-01

    从污染控制、润滑和密封三个方面研究了磁流变流体用作液压工作介质的可行性.配制了纳米铁粉磁流变流体,以此为介质,对设计的磁流变阀进行了实验研究.通过理论和实验研究表明该阀在小流量时可用作溢流阀;同时,该阀可以通过PWM方式实现对流量的控制.

  6. A rheological constitutive model for semiconcentrated rod suspensions in Bingham fluids

    Science.gov (United States)

    Férec, J.; Bertevas, E.; Khoo, B. C.; Ausias, G.; Phan-Thien, N.

    2017-07-01

    A rheological constitutive law is developed for a suspension of rigid rods in a Bingham fluid for volume fractions ranging up to the semiconcentrated regime. Based on a cell model approach, which allows expressing the shear stress on the particle surface, the particle stress contribution is derived and involves additional yield stress terms related to an ensemble average orientation distribution of the rods. As a first approach, a von Mises criterion is used to describe the composite flow threshold, which is found to be anisotropic in the sense that it depends on the rod orientation. A rod dynamics equation is also proposed and incorporates some diffusion/perturbation due to yielded regions encountered throughout the suspension. In parallel, an equivalent kinetic theory is also developed. The model provides good agreement with shear stress experiments for kaolin pastes filled with steel fibers of two different aspect ratios.

  7. Deformation and Break-up of Suspension Droplets Sheared in an Immiscible Fluid

    Science.gov (United States)

    Desse, Melinda; Hill, Sandra E.; Mitchell, John R.; Wolf, Bettina; Budtova, Tatiana

    2008-07-01

    The deformation and break-up behaviour of suspension droplets immersed in an immiscible fluid has not been widely studied albeit such systems are frequently encountered in every day multiphase products such as foods and cosmetics. Starch is a common thickener used in the food industry. Starch suspensions have shown to offer better flavour perception than polymer thickened solutions; a better understanding of their behaviour under flow would be beneficial in terms of advancement on product formulation. Deformation and break-up of a droplet of swollen-in-water starch granules placed in high viscosity silicon oil was visualised using a counter-rotating parallel-plate shear cell. The silicon oil had a high viscosity to induce shear stresses high enough to deform the droplet; it is also transparent and inert towards the studied system. The starch suspension was prepared to have a volume fraction of 100% swollen granules, i.e. that all water was bound within the swollen starch granules. The shear flow behaviour of this starch suspension is characterised by an apparent yield stress, shear-thinning and first normal stress differences. The rheo-optical experiments were conducted as start-up flow experiments applying shear stresses above the apparent yield stress. A constant shear stress throughout the experiment allows a constant viscosity of the droplet and therefore rules out the shear thinning aspect. Analysis showed droplet break-up at critical Capillary numbers close to those reported for Newtonian fluids. The results demonstrate that the droplet break-up behaviour in a complex emulsion system submitted to shear flow may not be fully described by the rheology of the individual phases alone but may require a microstructure component.

  8. High Performance Nanoparticle Fluid Suspensions (Nanofluids: A Future of Pharmaceutical Nanotechnology

    Directory of Open Access Journals (Sweden)

    M. S. Deodhar

    2014-10-01

    Full Text Available Pharmaceutical nanotechnology is evolved as a powerful tool for pharmaceutical chemist and formulation scientists. It has given a new direction to pharmaceutical and drug discovery research. Nanofluid technology which deals with nanofluids has provided an ultimate engineering solution for heat transfer application and automotive application in different industries. Nanofluids are engineered colloidal suspensions of nanoparticles in a base fluid. The nanoparticles used in nanofluids are typically made up of metals, oxides, carbides or carbon nanotubes. Common base fluids include water, ethylene glycol and oil. Preparation of nanofluids may be done by one step, two step method, chemical approach or laser ablation. The stability of nanofluids can be enhanced by different means such as addition surfactants, surface modification technique, pH control and ultrasonic agitation. Nanofluids are well known for their applications in engineering field, many researchers have also reported their use for different biological, medical and biomedical applications. Considering the tremendous growth of pharmaceutical nanotechnology with respect to drug discovery, formulation and development of nanoparticulate novel drug delivery systems, it is expected in coming years that high performance drug nanoparticle fluid suspensions (nanofluids will begin a new era of formulation research. This review article summarises method of preparation, characterization, stability, recent research and applications of nanofluids. It also identifies future scope of nanofluid technology for applications in pharmaceutical field.

  9. Direct evidence of entropy driven fluid-like - glass-like transition in microgel suspensions

    Science.gov (United States)

    Guo, Yun Xia; Liu, Ying Dan; Liu, Riping; Tian, Yongjun; Chen, Ke; Wang, Li-Min

    2017-02-01

    The phase transitions in poly (N-isopropylacrylamide) (PNIPAM) microgel suspensions are studied using rheological and calorimetric measurements at various concentrations. Two transitions are resolved, one being the hydrophilic-hydrophobic transition imposed by the gain/release of H2O molecules in PNIPAM particles via H-bond interactions, the other the fluid-like - glass-like transition of the hydrated microgels. The relaxation behaviors in the frozen glass-like states are observed by monitoring the shear modulus upon aging. Nevertheless, no enthalpic signature is detected in the relaxation process, suggesting entropy-driven relaxation dynamics.

  10. Particulate suspension Jeffrey fluid flow in a stenosed artery with a particle-free plasma layer near the wall

    Science.gov (United States)

    Ponalagusamy, R.

    2016-08-01

    The present article concerns the problem of blood flow through an artery with an axially asymmetric stenosis (constriction). The two-layered macroscopic model consisting of a cell-rich core of suspension of all the erythrocytes described as a particle-fluid suspension (Jeffrey fluid) and a peripheral zone of cell-free plasma (Newtonian fluid). The analytical expressions for flow characteristics such as fluid phase and particle phase velocities, flow rate, wall shear stress, and resistive force are obtained. It is of interest to mention that the magnitudes of wall shear stress and flow resistance increase with red cell concentration but the flow resistance decreases with increasing shape parameter. One of the important observations is that when blood behaves like a Jeffrey fluid, the flowing blood experiences lesser wall shear stress and flow resistance than in the case of blood being characterized as a Newtonian fluid in both the particle-fluid suspension and particle- free flow studies. The rheology of blood as Jeffrey fluid and the introduction of plasma layer thickness cause significant reduction in the magnitudes of the flow characteristics.

  11. Columnar structure formation of a dilute suspension of settling spherical particles in a quiescent fluid

    CERN Document Server

    Huisman, Sander G; Bourgoin, Mickaël; Chouippe, Agathe; Doychev, Todor; Huck, Peter; Morales, Carla E Bello; Uhlmann, Markus; Volk, Romain

    2016-01-01

    The settling of heavy spherical particles in a column of quiescent fluid is investigated. The performed experiments cover a range of Galileo numbers ($110 \\leq \\text{Ga} \\leq 310$) for a fixed density ratio of $\\Gamma = \\rho_p/\\rho_f = 2.5$. In this regime the particles are known (M. Jenny, J. Du\\v{s}ek and G. Bouchet, Journal of Fluid Mechanics 508, 201 (2004).) to show a variety of motions. It is known that the wake undergoes several transitions for increasing $\\text{Ga}$ resulting in particle motions that are successively: vertical, oblique, oblique oscillating, and finally chaotic. Not only does this change the trajectory of single, isolated, settling particles, but it also changes the dynamics of a swarm of particles as collective effects become important even for dilute suspensions, with volume fraction up to $\\Phi_V = \\mathcal{O}\\left(10^{-3}\\right)$, which are investigated in this work. Multi-camera recordings of settling particles are recorded and tracked over time in 3 dimensions. A variety of analy...

  12. Inverse neuro-fuzzy MR damper model and its application in vibration control of vehicle suspension system

    Science.gov (United States)

    Zong, Lu-Hang; Gong, Xing-Long; Guo, Chao-Yang; Xuan, Shou-Hu

    2012-07-01

    In this paper, a magneto-rheological (MR) damper-based semi-active controller for vehicle suspension is developed. This system consists of a linear quadratic Gauss (LQG) controller as the system controller and an adaptive neuro-fuzzy inference system (ANFIS) inverse model as the damper controller. First, a modified Bouc-Wen model is proposed to characterise the forward dynamic characteristics of the MR damper based on the experimental data. Then, an inverse MR damper model is built using ANFIS technique to determine the input current so as to gain the desired damping force. Finally, a quarter-car suspension model together with the MR damper is set up, and a semi-active controller composed of the LQG controller and the ANFIS inverse model is designed. Simulation results demonstrate that the desired force can be accurately tracked using the ANFIS technique and the semi-active controller can achieve competitive performance as that of active suspension.

  13. PREFACE: 13th International Conference on Electrorheological Fluids and Magnetorheological Suspensions (ERMR2012)

    Science.gov (United States)

    Unal, Halil Ibrahim

    2013-02-01

    Conference photograph The 13th International Conference on Electrorheological Fluids and Magnetorheological Suspensions (ERMR2012) was held in Ankara, Turkey at Gazi University in the Architect Kemaleddin historical hall on 2-6 July 2012. The first International Conference on Electrorheological Fluids and Magnetorheological Suspensions took place nearly 25 years ago and this conference continued the same tradition by providing an arena for researchers around the world to present their new research findings in these fields, and gave them the opportunity to learn about the latest research and technology and to renew their acquaintances. The meeting brought together scientists and engineers in multidisciplinary areas such as chemical engineering, mechanical engineering, materials science and engineering, physics, chemistry and polymer science and technology, to explore the state-of-art technology, identify key areas to be focused on and discuss their problems/issues. All oral presentations were held in a single session to enhance the interactions between the scientists and engineers. The ERMR2012 Conference included plenary lectures given by prominent leaders in their respective fields. About 130 participants from more than 50 organizations attended the conference and 15 plenary speeches, 64 oral presentations and 57 poster presentations took place in the following areas: (i) synthesis, characterization and processing of novel ER/MR materials, (ii) dynamics, chain and structure formation of ER/MR materials, (iii) ER/MR elastomers, ferrogels and their characterizations, (iv) rheological techniques and measurements of ER/MR materials, (v) modeling and simulations of ER/MR materials, (vi) device development and control techniques and (vii) applications of ER/MR materials. The ERMR2012 International Conference began with Turkish classical music performed by the musicians of the Ministry of Culture and Tourism. Rector Professor Dr R Ayhan welcomed the participants and the

  14. Columnar structure formation of a dilute suspension of settling spherical particles in a quiescent fluid

    Science.gov (United States)

    Huisman, Sander G.; Barois, Thomas; Bourgoin, Mickaël; Chouippe, Agathe; Doychev, Todor; Huck, Peter; Morales, Carla E. Bello; Uhlmann, Markus; Volk, Romain

    2016-11-01

    The settling of heavy spherical particles in a column of quiescent fluid is investigated. The performed experiments cover a range of Galileo numbers (110 ≤Ga≤310 ) for a fixed density ratio of Γ =ρp/ρf=2.5 . In this regime the particles are known to show a variety of motions [Jenny, Dušek, and Bouchet, Instabilities and transition of a sphere falling or ascending freely in a Newtonian fluid, J. Fluid Mech. 508, 201 (2004), 10.1017/S0022112004009164]. It is known that the wake undergoes several transitions for increasing Ga resulting in particle motions that are successively vertical, oblique, oblique oscillating, and finally chaotic. Not only does this change the trajectory of single, isolated, settling particles, but it also changes the dynamics of a swarm of particles as collective effects become important even for dilute suspensions with volume fraction up to ΦV=O (10-3) , which are investigated in this work. Multicamera recordings of settling particles are recorded and tracked over time in three dimensions. A variety of analyses are performed and show a strong clustering behavior. The distribution of the cell areas of the Voronoï tessellation in the horizontal plane is compared to that of a random distribution of particles and shows clear clustering. Moreover, a negative correlation was found between the Voronoï area and the particle velocity; clustered particles fall faster. In addition, the angle between adjacent particles and the vertical is calculated and compared to a homogeneous distribution of particles, clear evidence of vertical alignment of particles is found. The experimental findings are compared to simulations.

  15. Investigations concerning seismic response control of self-anchored suspension bridge with MR dampers

    Institute of Scientific and Technical Information of China (English)

    Menggang YANG; Zhengqing CHEN; Jianhua HU

    2008-01-01

    To mitigate the seismic response of selfanchored suspension bridges, equations of motion governing the coupled system of bridge- magneto-rheological (MR) dampers subject to seismic excitation are formulated by employing the phenomenological model of MR dampers. A corresponding computer program is developed and employed for studying the seismic response control of a self-anchored suspension bridge with a main span of 350 m. The effect of variable current and number of dampers on seismic response control is investigated. The numerical results indicate the longitudinal displacement of the tower top and bridge girder decrease with the increase in input current and number of MR dampers attached longitudinally at the tower-girder connections, and the internal forces of the tower are effectively attenuated as well. It appears that small electronic current (0.5 A in this study) may sufficiently attenuate the seismic responses for practical engineering applications.

  16. 磁流变阻尼器对近海风机的半主动控制研究%Study on Semi-active Control of Offshore Wind Turbines by Magneto-rheological Damper

    Institute of Scientific and Technical Information of China (English)

    李静; 陈健云; 柴健; 吕淑娟

    2013-01-01

    According to the vibration control problems of the offshore wind turbines under seismic load and wind load,the mechanical model of magneto-rheological (MR)damper and the relationship between the damping force and parameters of MR damper are presented here.The action principle of the fuzzy control algorithm in semi-active control is studied,and the Simulink simulation model is established,then the vibration control of the offshore wind turbines under the effects of seismic load and wind load is analyzed.For reducing the acceleration and displacement of the offshore wind turbines un-der the wind load and seismic load,the MR damper is used in the wind turbines.The result illustrates that this control method could effectively reduce the acceleration and displacement under the wind load and seismic load.%针对近海风机在地震动及风荷载联合作用下的振动控制问题,提出了基于磁流变阻尼器及模糊控制算法的半主动振动控制模型,研究了阻尼控制力与其构件参数之间的关系,并通过 Simulink 仿真模型对近海风机在地震荷载和风荷载作用下的振动控制进行了分析。计算结果表明,采用磁流变阻尼器能够有效的减小风荷载和地震荷载作用下近海风机结构的加速度和位移反应。

  17. Development of a suspension type sliding planar motion table using magnetic fluid lubrication

    Science.gov (United States)

    Li, Xinghui; Shinshi, Tadahiko; Hijikata, Wataru; Morimoto, Yoshihiro

    2016-06-01

    A sliding planar motion table system that can be used for the lens driving actuator of a laser cutting machine was developed. The system uses magnetic fluid as the lubricant to avoid the leakage of lubricating oil under the table and reduce environmental pollution. The motion table is suspended from the guide surface by an attractive force generated by electromagnets to reduce the contact and frictional forces between the table and the guide surface. The table is capable of movement in one rotational and two translational directions over the guide surface using six electromagnets and three non-contact displacement sensors. Experimental results showed that the magnetic suspension of the table reduced the friction by 82.1% compared to the friction that would otherwise be generated by the dead weight of the table. Circular motion within a diameter of 2 mm was achieved with resolutions of 5 μm and 20 μrad in the translational and rotational directions, respectively. A bandwidth of higher than 100 Hz was also achieved in the three movement directions.

  18. Impact of Single-Particle Compressibility on the Fluid-Solid Phase Transition for Ionic Microgel Suspensions

    Science.gov (United States)

    Pelaez-Fernandez, M.; Souslov, Anton; Lyon, L. A.; Goldbart, P. M.; Fernandez-Nieves, A.

    2015-03-01

    We study ionic microgel suspensions composed of swollen particles for various single-particle stiffnesses. We measure the osmotic pressure π of these suspensions and show that it is dominated by the contribution of free ions in solution. As this ionic osmotic pressure depends on the volume fraction of the suspension ϕ , we can determine ϕ from π , even at volume fractions so high that the microgel particles are compressed. We find that the width of the fluid-solid phase coexistence, measured using ϕ , is larger than its hard-sphere value for the stiffer microgels that we study and progressively decreases for softer microgels. For sufficiently soft microgels, the suspensions are fluidlike, irrespective of volume fraction. By calculating the dependence on ϕ of the mean volume of a microgel particle, we show that the behavior of the phase-coexistence width correlates with whether or not the microgel particles are compressed at the volume fractions corresponding to fluid-solid phase coexistence.

  19. Fluid flow phenomena in the generation of boron carbide suspensions in magnesium melts

    Science.gov (United States)

    Ilegbusi, O. J.; Szekely, J.

    1988-01-01

    A mathematical representation is developed for the behavior of moderately concentrated magnesium-boron carbide suspensions when subjected to electromagnetic stirring or mechanical agitation. A power-law relationship is employed for the apparent non-Newtonian viscosity of the suspension.

  20. Multi-objective Optimization for the Magnetic Circuit of Magneto-rheological Mount Based on NSGA-II Algorithm%基于NSGA-II算法的磁流变悬置磁路多目标优化

    Institute of Scientific and Technical Information of China (English)

    邓召学; 郑玲; 李以农; 张东东; 付江华; 陈代军

    2015-01-01

    With minimizing the volume of magnetic circuit structure and maximizing its output damping force as optimization objectives, a multi-objective optimization model for the magnetic circuit structure of magneto-rheological ( MR) mount is established with ANSYS parametric design language ( APDL) . An optimization is con-ducted with the fast elitist non-dominated sorting genetic algorithm ( NSGA-II) and a pareto optimal set is obtained, from which the best compromise solution is extracted based on fuzzy set theory. Two MR mounts with magnetic cir-cuit structures before and after optimization are manufactured respectively and tested on their dynamic performance. The results show that the multi-objective optimization scheme proposed is correct and effective in achieving a more compact magnetic circuit structure with an increased output damping force.%以磁流变悬置的磁路体积最小、输出阻尼力最大为优化目标,基于ANSYS参数化设计语言( APDL)建立了磁流变悬置磁路结构的多目标优化模型,采用带精英策略的快速非支配排序遗传算法( NSGA-II)进行优化,获得了磁路结构的Pareto最优解,并采用模糊集合理论对Pareto最优解进行选优。根据优化前后的磁路结构尺寸加工了两个磁流变悬置,并对悬置动态性能进行试验。结果表明:所提出的磁流变悬置磁路多目标优化方法是正确有效的,能够获得更加紧凑的磁流变悬置磁路结构,并提高悬置的输出阻尼力。

  1. An experimental study of convective heat transfer, friction, and rheology for non-Newtonian fluids: Polymer solutions, suspensions of fibers, and suspensions of particulates

    Science.gov (United States)

    Matthys, E. F.

    The convective heat transfer, friction, and rheological properties of various types of nonNewtonian fluid in circular tube flows were investigated. If an apparent Reynolds number is used and if the temperature and degradation effects are properly taken into account, the reduced turbulent friction and heat transfer results, respectively, are then shown to be well correlated by the same expressions for different fluids, regardless of the nature of the fluids and whether they are shear-thinning or shear-thickening. This representation can also separate the reductions in turbulent heat transfer and friction that are induced by viscoelasticity from those induced by pseudoplasticity. Polyacrylamide solutions inducing asymptotic and intermediate drag reduction regimes were investigated over a broad range of Reynolds numbers. A kerosene-based antimisting polymer solution was also studied. Suspensions of bentonite of various concentrations were investigated in laminar and turbulent regimes, and the results for fully developed and entrance flows were well correlated by Newtonian relationships when an adequate wall viscosity concept was used.

  2. H∞ control of railway vehicle suspension with MR damper using scaled roller rig

    Science.gov (United States)

    Shin, Yu-Jeong; You, Won-Hee; Hur, Hyun-Moo; Park, Joon-Hyuk

    2014-09-01

    In this paper, a magneto-rheological (MR) damper was applied to the secondary suspension to reduce the vibration of a car body. The control performance of the MR damper was verified by numerical analysis with a 1/5 scale railway vehicle model in accordance with the similarity law. The analysis results were then validated in tests. In particular, the objective of the study was to understand how the control performance affected the dynamic characteristics of a railway vehicle and to systematically analyze the relationship between control performance and dynamic characteristics depending on various running speeds. To achieve this, experimental results for the dynamic characteristics of the scaled MR damper designed for the 1/5 scale railway vehicle model were applied to the railway vehicle model. The H∞ control method was applied to the controller. The means of designing the railway vehicle body vibration controller and the effectiveness of its results were studied.

  3. Ride performance of a high speed rail vehicle using controlled semi active suspension system

    Science.gov (United States)

    Sharma, Sunil Kumar; Kumar, Anil

    2017-05-01

    The rail-wheel interaction in a rail vehicle running at high speed results in large amplitude vibration of carbody that deteriorates the ride comfort of travellers. The role of suspension system is crucial to provide an acceptable level of ride performance. In this context, an existing rail vehicle is modelled in vertical, pitch and roll motions of carbody and bogies. Additionally, nonlinear stiffness and damping parameters of passive suspension system are defined based on experimental data. In the secondary vertical suspension system, a magneto-rheological (MR) damper is included to improve the ride quality and comfort. The parameters of MR damper depend on the current, amplitude and frequency of excitations. At different running speeds, three semi-active suspension strategies with MR damper are analysed for periodic track irregularity and the resulting performance indices are juxtaposed with the nonlinear passive suspension system. The disturbance rejection and force tracking damper controller algorithms are applied to control the desired force of MR damper. This study reveals that the vertical vibrations of a vehicle can be reduced significantly by using the proposed semi-active suspension strategies. Moreover, it naturally results in improved ride quality and passenger’s comfort in comparison to the existing passive system.

  4. Delivery of vegetable oil suspensions in a shear thinning fluid for enhanced bioremediation

    Science.gov (United States)

    Zhong, L.; Truex, M. J.; Kananizadeh, N.; Li, Y.; Lea, A. S.; Yan, X.

    2015-04-01

    In situ anaerobic biological processes are widely applied for dechlorination of chlorinated solvents in groundwater. A wide range of organic substrates have been tested and applied to support the dechlorination processes. Vegetable oils are a promising type of substrate and have been shown to induce effective dechlorination, have limited geochemical impacts, and maintain good longevity. Because they are non-aqueous phase liquids, distribution of vegetable oils in the subsurface has typically been approached by creating emulsified oil solutions for injection into the aquifer. In this study, inexpensive waste vegetable oils were suspended in a shear-thinning xanthan gum solution as an alternative approach for delivery of vegetable oil to the subsurface. The stability, oil droplet size distribution, and rheological behavior of the oil suspensions that are created in the xanthan solutions were studied in batch experiments. The injectability of the suspensions and the oil distribution in a porous medium were evaluated in column tests. Numerical modeling of oil droplet transport and distribution in porous media was conducted to help interpret the column-test data. Batch studies showed that simple mixing of vegetable oil with xanthan solution produced stable suspensions of the oil as micron-size droplets. The mixture rheology retains shear-thinning properties that facilitate improved uniformity of substrate distribution in heterogeneous aquifers. Column tests demonstrated successful injection of the vegetable oil suspension into a porous medium. This study provides evidence that vegetable oil suspensions in xanthan gum solutions have favorable injection properties and are a potential substrate for in situ anaerobic bioremediation.

  5. Rheology and fluid mechanics of a hyper-concentrated biomass suspension

    Science.gov (United States)

    Botto, Lorenzo; Xu, Xiao

    2013-11-01

    The production of bioethanol from biomass material originating from energy crops requires mixing of highly concentrated suspensions, which are composed of millimetre-sized lignocellulosic fibers. In these applications, the solid concentration is typically extremely high. Owing to the large particle porosity, for a solid mass concentration slightly larger than 10%, the dispersed solid phase can fill the available space almost completely. To extract input parameters for simulations, we have carried out rheological measurements of a lignocellulosic suspension of Miscanthus, a fast-growing plant, for particle concentrations close to maximum random packing. We find that in this regime the rheometric curves exhibit features similar to those observed in model ``gravitational suspensions,'' including viscoplastic behaviour, strong shear-banding, non-continuum effects, and a marked influence of the particle weight. In the talk, these aspects will be examined in some detail, and differences between Miscanthus and corn stover, currently the most industrially relevant biomass substrate, briefly discussed. We will also comment on values of the Reynolds and Oldroyd numbers found in biofuel applications, and the flow patterns expected for these parameter values.

  6. Ghost Cell Suspensions as Blood Analogue Fluid for Macroscopic Particle Image Velocimetry Measurements.

    Science.gov (United States)

    Jansen, Sebastian V; Müller, Indra; Nachtsheim, Max; Schmitz-Rode, Thomas; Steinseifer, Ulrich

    2016-02-01

    Spatially resolved measurement of blood flow is of great interest in the development of artificial blood-carrying devices such as blood pumps, heart valve prostheses, and oxygenators. Particle image velocimetry (PIV) is able to measure instantaneous velocity fields in a plane with high accuracy and is being used more frequently for the development of such devices. However, as this measurement technique is based on optical access, blood flow at physiological hematocrit values is difficult to measure due to its low transparency and multiscattering properties. So far, only very small dimensions (in the range of 400 μm) can be measured using PIV. A suspension of ghost cells (GCs) offers a higher optical transparency than blood while having a similar rheological behavior. In this study, a procedure for the production of GC suspensions containing a very low intracellular hemoglobin concentration is presented. With the help of multiple rounds of controlled cell lysis, the intracellular hemoglobin concentration could be decreased to a point where a standard macroscopic PIV measurement was possible. A velocity profile of a 44% GC suspension in a circular channel with a diameter of 9.5 mm was measured with high spatial resolution. Meanwhile, the rheological behavior was found to be comparable with blood.

  7. Effect of viscous dissipation on hydromagnetic fluid flow and heat transfer of nanofluid over an exponentially stretching sheet with fluid-particle suspension

    Directory of Open Access Journals (Sweden)

    M.R. Krishnamurthy

    2015-12-01

    Full Text Available This paper considers the problem of steady, boundary layer flow and heat transfer of a nanofluid with fluid-particle suspension over an exponentially stretching surface in the presence of transverse magnetic field and viscous dissipation. The stretching velocity and wall temperature are assumed to vary according to specific exponential form. The governing equations in partial forms are reduced to a system of coupled non-linear ordinary differential equations using suitable similarity transformations. An effective Runge–Kutta–Fehlberg (RKF-45 is used to solve the obtained differential equations with the help of a symbolic software MAPLE. The effects of flow parameters—such as nanofluid interaction parameter, magnetic parameter, solid volume fraction of nanoparticle parameter, Prandtl number and Eckert number—on the flow field and heat-transfer characteristics were obtained and are tabulated. Useful discussions were carried out with the help of plotted graphs and tables. Under the limiting cases, comparison with the existing results was made and found to be in good agreement. The results demonstrate that the skin friction coefficient increases for both magnetic and solid volume fraction nanoparticle parameters. However, dusty fluid with copper (Cu nanoparticles has the appreciable cooling performance than other fluids.

  8. Heat transfer analysis on peristaltically induced motion of particle-fluid suspension with variable viscosity: Clot blood model.

    Science.gov (United States)

    Bhatti, M M; Zeeshan, A; Ellahi, R

    2016-12-01

    In this article, heat transfer analysis on clot blood model of the particle-fluid suspension through a non-uniform annulus has been investigated. The blood propagating along the whole length of the annulus was induced by peristaltic motion. The effects of variable viscosity and slip condition are also taken into account. The governing flow problem is modeled using lubrication approach by taking the assumption of long wavelength and creeping flow regime. The resulting equation for fluid phase and particle phase is solved analytically and closed form solutions are obtained. The physical impact of all the emerging parameters is discussed mathematically and graphically. Particularly, we considered the effects of particle volume fraction, slip parameter, the maximum height of clot, viscosity parameter, average volume flow rate, Prandtl number, Eckert number and fluid parameter on temperature profile, pressure rise and friction forces for outer and inner tube. Numerical computations have been used to determine the behavior of pressure rise and friction along the whole length of the annulus. The present study is also presented for an endoscope as a special case of our study. It is observed that greater influence of clot tends to rise the pressure rise significantly. It is also found that temperature profile increases due to the enhancement in Prandtl number, Eckert number, and fluid parameter. The present study reveals that friction forces for outer tube have higher magnitude as compared to the friction forces for an inner tube. In fact, the results for present study can also be reduced to the Newtonian fluid by taking ζ → ∞.

  9. Stable suspension and dispersion-induced transitions from repulsive Casimir forces between fluid separated eccentric cylinders

    Energy Technology Data Exchange (ETDEWEB)

    Dalvit, Diego A1 [Los Alamos National Laboratory; Rodriguez, Alejandro W [MASS INST OF TECH; Munday, J N [HARVARD UNIV; Joannopoulos, J D [MASS INST OF TECH

    2008-01-01

    Using accurate numerical methods for finite-size nonplanar objects, we demonstrate a stable mechanical suspension of a silica cylinder within a metallic cylinder separated by ethanol, via a repulsive Casimir force between the silica and the metal. We investigate cylinders with both circular and square cross sections, and show that the latter exhibit a stable orientation as well as a stable position, employing a new method to accurately compute Casimir torques for finite objects. Furthermore, the stable orientation of the square cylinder is shown to undergo an unusual 45 transition as a function of the separation lengthscale, and this transition is explained as a consequence of material dispersion.

  10. Equilibrium fluid-crystal interfacial free energy of bcc-crystallizing aqueous suspensions of polydisperse charged spheres.

    Science.gov (United States)

    Palberg, Thomas; Wette, Patrick; Herlach, Dieter M

    2016-02-01

    The interfacial free energy is a central quantity in crystallization from the metastable melt. In suspensions of charged colloidal spheres, nucleation and growth kinetics can be accurately measured from optical experiments. In previous work, from these data effective nonequilibrium values for the interfacial free energy between the emerging bcc nuclei and the adjacent melt in dependence on the chemical potential difference between melt phase and crystal phase were derived using classical nucleation theory (CNT). A strictly linear increase of the interfacial free energy was observed as a function of increased metastability. Here, we further analyze these data for five aqueous suspensions of charged spheres and one binary mixture. We utilize a simple extrapolation scheme and interpret our findings in view of Turnbull's empirical rule. This enables us to present the first systematic experimental estimates for a reduced interfacial free energy, σ(0,bcc), between the bcc-crystal phase and the coexisting equilibrium fluid. Values obtained for σ(0,bcc) are on the order of a few k(B)T. Their values are not correlated to any of the electrostatic interaction parameters but rather show a systematic decrease with increasing size polydispersity and a lower value for the mixture as compared to the pure components. At the same time, σ(0) also shows an approximately linear correlation to the entropy of freezing. The equilibrium interfacial free energy of strictly monodisperse charged spheres may therefore be still greater.

  11. Low hazard refractive index and density-matched fluid for quantitative imaging of concentrated suspensions of particles

    Science.gov (United States)

    Zhu, W.; Knapp, Y.; Deplano, V.

    2016-05-01

    A novel refractive index and density-matched liquid-solid suspension system taking into account chemical hazard and health concerns was developed and characterized. The solid phase is made of PMMA spheres, the refractive index of which being adapted with a mixture of 2,2'-thiodiethanol and phosphate-buffered saline (PBS), while the density is adapted with a mixture of PBS and glycerol. The proposed chemicals present low hazard characteristics in comparison with former solutions. Data collected from density and refractive index measurements of the solid phase and of the different fluid constituents are used to define a specific ternary mixture adapted to commercial grade micron-size particles. The defined mixture is validated in a micron-sized granular flow experiment. The described method can be applied to other low-density solids.

  12. Apparatus for accurate density measurements of fluids based on a magnetic suspension balance

    Science.gov (United States)

    Gong, Maoqiong; Li, Huiya; Guo, Hao; Dong, Xueqiang; Wu, J. F.

    2012-06-01

    A new apparatus for accurate pressure, density and temperature (p, ρ, T) measurements over wide ranges of (p, ρ, T) (90 K to 290 K; 0 MPa to 3 MPa; 0 kg/m3 to 2000 kg/m3) is described. This apparatus is based on a magnetic suspension balance which applies the Archimedes' buoyancy principle. In order to verify the new apparatus, comprehensive (p, ρ, T) measurements on pure nitrogen were carried out. The maximum relative standard uncertainty is 0.09% in density. The maximum standard uncertainty in temperature is 5 mK, and that in pressure is 250 Pa for 1.5 MPa and 390 Pa for 3MPa full scale range respectively. The experimental data were compared with selected literature data and good agreements were found.

  13. H2 control of a one-quarter semi-active ground vehicle suspension

    Directory of Open Access Journals (Sweden)

    L.C. Félix-Herrán

    2016-06-01

    Full Text Available Magneto-rheological (MR dampers are effective solutions in improving vehicle stability and passenger comfort. However, handling these dampers implies a strong effort in modeling and control. This research proposes an H2 controller, based on a Takagi–Sugeno (T–S fuzzy model, for a two-degrees-of-freedom (2-DOF one-quarter vehicle semi-active suspension with an MR damper; a system with important applications in automotive industry. Regarding performance criteria (in frequency domain handled herein, the developed controller considerably improves the passive suspension's efficiency. Moreover, nonlinear actuator dynamics usually avoided in reported work, is included in controller's synthesis; improving the relevance of research outcomes because the controller is synthesized from a closer-to-reality suspension model. Going further, outcomes of this research are compared (based on frequency domain performance criteria and a common time domain test with reported work to highlight the outstanding results. H2 controller is given in terms of quadratic Lyapunov stability theory and carried out by means of Linear Matrix Inequalities (LMI, and the command signal is applied via the Parallel Distributed Compensation (PDC approach. A case of study, with real data, is developed and simulation work supports the results. The methodology applied herein can be extended to include other vehicle suspension's dynamics towards a general chassis control.

  14. Research on Shock Control Technology of Magneto-rheological Fluid Shock Absorption%磁流变液减振器及其振动控制技术概述

    Institute of Scientific and Technical Information of China (English)

    蔡洪伟; 李凌辉; 谢友宝

    2008-01-01

    在振动控制领域,基于新型磁流变液材料制成的减振器正得到越来越广泛的应用,应用磁流变液减振器对机械设备进行减振防护是近年来减振技术研究的热点之一.阐述磁流变减振器的类型及技术特点,对比几种常用的振动控制方法的优异性,讨论磁流变减振器的实用价,指出磁流变液减振器是目前减振设备的开发方向.

  15. Blood flow of Jeffrey fluid in a catherized tapered artery with the suspension of nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Ellahi, R., E-mail: rellahi@engr.ucr.edu [Department of Mechanical Engineering, University of California Riverside (United States); Department of Mathematics and Statistics, FBAS, IIU, Islamabad (Pakistan); Rahman, S.U. [Department of Mathematics and Statistics, FBAS, IIU, Islamabad (Pakistan); Nadeem, S. [Department of Mathematics, Quaid-i-Azam University Islamabad (Pakistan)

    2014-08-14

    Current letter deals with the mathematical models of Jeffrey fluid via nanoparticles in the tapered stenosed atherosclerotic arteries. The convection effects of heat transfer with catheter are also taken into account. The nonlinear coupled equations of nanofluid model are simplified under mild stenosis. The solutions for concentration and temperature are found by using homotopy perturbation method, whereas for velocity profile the exact solution is calculated. Moreover, the expressions for flow impedance and pressure rise are computed and discussed through graphs for different physical quantities of interest. The streamlines have also been presented to discuss the trapping bolus discipline.

  16. Blood flow of Jeffrey fluid in a catherized tapered artery with the suspension of nanoparticles

    Science.gov (United States)

    Ellahi, R.; Rahman, S. U.; Nadeem, S.

    2014-08-01

    Current letter deals with the mathematical models of Jeffrey fluid via nanoparticles in the tapered stenosed atherosclerotic arteries. The convection effects of heat transfer with catheter are also taken into account. The nonlinear coupled equations of nanofluid model are simplified under mild stenosis. The solutions for concentration and temperature are found by using homotopy perturbation method, whereas for velocity profile the exact solution is calculated. Moreover, the expressions for flow impedance and pressure rise are computed and discussed through graphs for different physical quantities of interest. The streamlines have also been presented to discuss the trapping bolus discipline.

  17. Rheological behavior of clay-nanoparticle hybrid-added bentonite suspensions: specific role of hybrid additives on the gelation of clay-based fluids.

    Science.gov (United States)

    Jung, Youngsoo; Son, You-Hwan; Lee, Jung-Kun; Phuoc, Tran X; Soong, Yee; Chyu, Minking K

    2011-09-01

    Two different types of clay nanoparticle hybrid, iron oxide nanoparticle clay hybrid (ICH) and Al(2)O(3)-SiO(2) nanoparticle clay hybrid (ASCH), were synthesized and their effects on the rheological properties of aqueous bentonite fluids in steady state and dynamic state were explored. When ICH particles were added, bentonite particles in the fluid cross-link to form relatively well-oriented porous structure. This is attributed to the development of positively charged edge surfaces in ICH that leads to strengthening of the gel structure of the bentonite susensions. The role of ASCH particles on the interparticle association of the bentonite fluids is different from that of ICH and sensitive to pH. As pH of ASCH-added bentonite suspensions increased, the viscosity, yield stress, storage modulus, and flow stress decreased. In contrast, at low pH, the clay suspensions containing ASCH additives were coagulated and their rheological properties become close to those of ICH added bentonite fluids. A correlation between the net surface charge of the hybrid additives and the rheological properties of the fluids indicates that the embedded nanoparticles within the interlayer space control the variable charge of the edge surfaces of the platelets and determine the particles association behavior of the clay fluids.

  18. Sterically stabilized water based magnetic fluids: Synthesis, structure and properties

    Science.gov (United States)

    Bica, Doina; Vékás, Ladislau; Avdeev, Mikhail V.; Marinică, Oana; Socoliuc, Vlad; Bălăsoiu, Maria; Garamus, Vasil M.

    2007-04-01

    Magnetic fluids (MFs), prepared by chemical co-precipitation followed by double layer steric and electrostatic (combined) stabilization of magnetite nanoparticles dispersed in water, are presented. Several combinations of surfactants with different chain lengths (lauric acid (LA), myristic acid (MA), oleic acid (OA) and dodecyl-benzene-sulphonic acid (DBS)) were used, such as LA+LA, MA+MA, LA+DBS, MA+DBS, OA+DBS, OA+OA and DBS+DBS. Static light scattering, transmission electron microscopy, small angle neutron scattering, magnetic and magneto-rheological measurements revealed that MFs with MA+MA or LA+LA biocompatible double layer covered magnetite nanoparticles are the most stable colloidal systems among the investigated samples, and thus suitable for biomedical applications.

  19. Sterically stabilized water based magnetic fluids: Synthesis, structure and properties

    Energy Technology Data Exchange (ETDEWEB)

    Bica, Doina [Laboratory of Magnetic Fluids, Center for Fundamental and Advanced Technical Research, Romanian Academy, Timisoara Division, Bd. Mihai Viteazul 24, 300223 Timisoara (Romania); Vekas, Ladislau [Laboratory of Magnetic Fluids, Center for Fundamental and Advanced Technical Research, Romanian Academy, Timisoara Division, Bd. Mihai Viteazul 24, 300223 Timisoara (Romania) and National Centre for Engineering of Systems with Complex Fluids, University Politehnica Timisoara, Bd. Mihai Viteazul 1, 300222 Timisoara (Romania)]. E-mail: vekas@acad-tim.tm.edu.ro; Avdeev, Mikhail V. [Frank Laboratory of Neutron Physics, Joint Institute for Nuclear Research, Dubna (Russian Federation); Marinica, Oana [National Centre for Engineering of Systems with Complex Fluids, University Politehnica Timisoara, Bd. Mihai Viteazul 1, 300222 Timisoara (Romania); Socoliuc, Vlad [National Institute R and D for Electrochemistry and Condensed Matter, Str. Diaconu Coressi 144, 300588 Timisoara (Romania); Balasoiu, Maria [Frank Laboratory of Neutron Physics, Joint Institute for Nuclear Research, Dubna (Russian Federation); Garamus, Vasil M. [GKSS Research Centre, Geesthacht (Germany)

    2007-04-15

    Magnetic fluids (MFs), prepared by chemical co-precipitation followed by double layer steric and electrostatic (combined) stabilization of magnetite nanoparticles dispersed in water, are presented. Several combinations of surfactants with different chain lengths (lauric acid (LA), myristic acid (MA), oleic acid (OA) and dodecyl-benzene-sulphonic acid (DBS)) were used, such as LA+LA, MA+MA, LA+DBS, MA+DBS, OA+DBS, OA+OA and DBS+DBS. Static light scattering, transmission electron microscopy, small angle neutron scattering, magnetic and magneto-rheological measurements revealed that MFs with MA+MA or LA+LA biocompatible double layer covered magnetite nanoparticles are the most stable colloidal systems among the investigated samples, and thus suitable for biomedical applications.

  20. Unsteady MHD two-phase Couette flow of fluid-particle suspension in an annulus

    Directory of Open Access Journals (Sweden)

    Basant K. Jha

    2011-12-01

    Full Text Available The problem of two-phase unsteady MHD flow between two concentric cylinders of infinite length has been analysed when the outer cylinder is impulsively started. The system of partial differential equations describing the flow problem is formulated taking the viscosity of the particle phase into consideration. Unified closed form expressions are obtained for the velocities and the skin frictions for both cases of the applied magnetic field being fixed to either the fluid or the moving outer cylinder. The problem is solved using a combination of the Laplace transform technique, D’Alemberts and the Riemann-sum approximation methods. The solution obtained is validated by comparisons with the closed form solutions obtained for the steady states which has been derived separately. The governing equations are also solved using the implicit finite difference method to verify the present proposed method. The variation of the velocity and the skin friction with the dimensionless parameters occuring in the problem are illustrated graphically and discussed for both phases.

  1. Theory of activated penetrant diffusion in viscous fluids and colloidal suspensions.

    Science.gov (United States)

    Zhang, Rui; Schweizer, Kenneth S

    2015-10-14

    We heuristically formulate a microscopic, force level, self-consistent nonlinear Langevin equation theory for activated barrier hopping and non-hydrodynamic diffusion of a hard sphere penetrant in very dense hard sphere fluid matrices. Penetrant dynamics is controlled by a rich competition between force relaxation due to penetrant self-motion and collective matrix structural (alpha) relaxation. In the absence of penetrant-matrix attraction, three activated dynamical regimes are predicted as a function of penetrant-matrix size ratio which are physically distinguished by penetrant jump distance and the nature of matrix motion required to facilitate its hopping. The penetrant diffusion constant decreases the fastest with size ratio for relatively small penetrants where the matrix effectively acts as a vibrating amorphous solid. Increasing penetrant-matrix attraction strength reduces penetrant diffusivity due to physical bonding. For size ratios approaching unity, a distinct dynamical regime emerges associated with strong slaving of penetrant hopping to matrix structural relaxation. A crossover regime at intermediate penetrant-matrix size ratio connects the two limiting behaviors for hard penetrants, but essentially disappears if there are strong attractions with the matrix. Activated penetrant diffusivity decreases strongly with matrix volume fraction in a manner that intensifies as the size ratio increases. We propose and implement a quasi-universal approach for activated diffusion of a rigid atomic/molecular penetrant in a supercooled liquid based on a mapping between the hard sphere system and thermal liquids. Calculations for specific systems agree reasonably well with experiments over a wide range of temperature, covering more than 10 orders of magnitude of variation of the penetrant diffusion constant.

  2. Theory of activated penetrant diffusion in viscous fluids and colloidal suspensions

    Science.gov (United States)

    Zhang, Rui; Schweizer, Kenneth S.

    2015-10-01

    We heuristically formulate a microscopic, force level, self-consistent nonlinear Langevin equation theory for activated barrier hopping and non-hydrodynamic diffusion of a hard sphere penetrant in very dense hard sphere fluid matrices. Penetrant dynamics is controlled by a rich competition between force relaxation due to penetrant self-motion and collective matrix structural (alpha) relaxation. In the absence of penetrant-matrix attraction, three activated dynamical regimes are predicted as a function of penetrant-matrix size ratio which are physically distinguished by penetrant jump distance and the nature of matrix motion required to facilitate its hopping. The penetrant diffusion constant decreases the fastest with size ratio for relatively small penetrants where the matrix effectively acts as a vibrating amorphous solid. Increasing penetrant-matrix attraction strength reduces penetrant diffusivity due to physical bonding. For size ratios approaching unity, a distinct dynamical regime emerges associated with strong slaving of penetrant hopping to matrix structural relaxation. A crossover regime at intermediate penetrant-matrix size ratio connects the two limiting behaviors for hard penetrants, but essentially disappears if there are strong attractions with the matrix. Activated penetrant diffusivity decreases strongly with matrix volume fraction in a manner that intensifies as the size ratio increases. We propose and implement a quasi-universal approach for activated diffusion of a rigid atomic/molecular penetrant in a supercooled liquid based on a mapping between the hard sphere system and thermal liquids. Calculations for specific systems agree reasonably well with experiments over a wide range of temperature, covering more than 10 orders of magnitude of variation of the penetrant diffusion constant.

  3. Theory of activated penetrant diffusion in viscous fluids and colloidal suspensions

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Rui; Schweizer, Kenneth S., E-mail: kschweiz@illinois.edu [Department of Materials Science and Frederick Seitz Materials Research Laboratory, University of Illinois, 1304 West Green Street, Urbana, Illinois 61801 (United States)

    2015-10-14

    We heuristically formulate a microscopic, force level, self-consistent nonlinear Langevin equation theory for activated barrier hopping and non-hydrodynamic diffusion of a hard sphere penetrant in very dense hard sphere fluid matrices. Penetrant dynamics is controlled by a rich competition between force relaxation due to penetrant self-motion and collective matrix structural (alpha) relaxation. In the absence of penetrant-matrix attraction, three activated dynamical regimes are predicted as a function of penetrant-matrix size ratio which are physically distinguished by penetrant jump distance and the nature of matrix motion required to facilitate its hopping. The penetrant diffusion constant decreases the fastest with size ratio for relatively small penetrants where the matrix effectively acts as a vibrating amorphous solid. Increasing penetrant-matrix attraction strength reduces penetrant diffusivity due to physical bonding. For size ratios approaching unity, a distinct dynamical regime emerges associated with strong slaving of penetrant hopping to matrix structural relaxation. A crossover regime at intermediate penetrant-matrix size ratio connects the two limiting behaviors for hard penetrants, but essentially disappears if there are strong attractions with the matrix. Activated penetrant diffusivity decreases strongly with matrix volume fraction in a manner that intensifies as the size ratio increases. We propose and implement a quasi-universal approach for activated diffusion of a rigid atomic/molecular penetrant in a supercooled liquid based on a mapping between the hard sphere system and thermal liquids. Calculations for specific systems agree reasonably well with experiments over a wide range of temperature, covering more than 10 orders of magnitude of variation of the penetrant diffusion constant.

  4. Combustion, Complex Fluids, and Fluid Physics Experiments on the ISS

    Science.gov (United States)

    Motil, Brian; Urban, David

    2012-01-01

    From the very first days of human spaceflight, NASA has been conducting experiments in space to understand the effect of weightlessness on physical and chemically reacting systems. NASA Glenn Research Center (GRC) in Cleveland, Ohio has been at the forefront of this research looking at both fundamental studies in microgravity as well as experiments targeted at reducing the risks to long duration human missions to the moon, Mars, and beyond. In the current International Space Station (ISS) era, we now have an orbiting laboratory that provides the highly desired condition of long-duration microgravity. This allows continuous and interactive research similar to Earth-based laboratories. Because of these capabilities, the ISS is an indispensible laboratory for low gravity research. NASA GRC has been actively involved in developing and operating facilities and experiments on the ISS since the beginning of a permanent human presence on November 2, 2000. As the lead Center both Combustion, Fluid Physics, and Acceleration Measurement GRC has led the successful implementation of an Acceleration Measurement systems, the Combustion Integrated Rack (CIR), the Fluids Integrated Rack (FIR) as well as the continued use of other facilities on the ISS. These facilities have supported combustion experiments in fundamental droplet combustion fire detection fire extinguishment soot phenomena flame liftoff and stability and material flammability. The fluids experiments have studied capillary flow magneto-rheological fluids colloidal systems extensional rheology pool and nucleate boiling phenomena. In this paper, we provide an overview of the experiments conducted on the ISS over the past 12 years. We also provide a look to the future development. Experiments presented in combustion include areas such as droplet combustion, gaseous diffusion flames, solid fuels, premixed flame studies, fire safety, and super critical oxidation processes. In fluid physics, experiments are discussed in

  5. Boundary Layer Flow and Heat Transfer of fluid particle suspension with nanoparticles over a nonlinear stretching sheet embedded in a porous medium

    Science.gov (United States)

    Prasannakumara, B. C.; Shashikumar, N. S.; Venkatesh, P.

    2017-09-01

    An analysis has been carried out to study the effect of nonlinear thermal radiation on slip flow and heat transfer of fluid particle suspension with nanoparticles over a nonlinear stretching sheet immersed in a porous medium. Water is considered as a base fluid with dust particles along with suspended Aluminum Oxide (Al2O3) nanoparticles. Using appropriate similarity transformations, the coupled nonlinear partial differential equations are reduced into a set of coupled nonlinear ordinary differential equations. The reduced equations are then solved numerically using Runge-Kutta-Fehlberg45 order method with the help of shooting technique to investigate the impact of various pertinent parameters for the velocity and temperature fields. The obtained results are presented in tabular form as well as graphically and discussed in detail. Effect of different parameters on skin friction coefficient and Nusselt number are also discussed.

  6. Energy dissipation control of magneto-rheological damper

    DEFF Research Database (Denmark)

    Høgsberg, Jan Becker; Krenk, Steen

    2008-01-01

    The efficiency of a damper depends on the amount of energy dissipation during a typical cycle experienced by the damper. For viscous dampers this leads to substantial frequency dependence. For dampers with hysteresis the tuning and efficiency also depends on the apparent amplitude of the damper...... response. For irregular damper response the amplitude is evaluated as the magnitude of closed hysteresis loops. These loops are identified in real time by the rainflow rules, stored in a Markov-type matrix and used to predict the magnitude of subsequent closed loops. From this prediction the properties...

  7. Paradoxical ratcheting in cornstarch suspensions

    Science.gov (United States)

    Shinbrot, Troy; Siu, Theo; Rutala, Matthew

    2014-11-01

    Cornstarch suspensions are well known to exhibit strong shear thickening, and we show as a result that they must - and do - climb vertically vibrating rods and plates. This occurs because when the rod moves upward, it shears the suspension against gravity, and so the fluid stiffens, but when the rod moves downward, the suspension moves with gravity, and so the fluid is more compliant. This causes the fluid to be dragged up by the upstroke more than it is dragged down by the downstroke, effectively ratcheting the fluid up the rod every cycle. We show experimentally and computationally that this effect is paradoxically caused by gravity - and so goes away when gravity is removed - and we show that the suspension can be made to balance on the uphill side of an inclined rod in an analog of the inverted ``Kapitza pendulum,'' closely related to the recent report by Ramachandran & Nosonovsky, Soft Matter 10, 4633 (2014).

  8. A Comprehensive Review on Fluid Dynamics and Transport of Suspension/Liquid Droplets and Particles in High-Velocity Oxygen-Fuel (HVOF Thermal Spray

    Directory of Open Access Journals (Sweden)

    Mehdi Jadidi

    2015-10-01

    Full Text Available In thermal spraying processes, molten, semi-molten, or solid particles, which are sufficiently fast in a stream of gas, are deposited on a substrate. These particles can plastically deform while impacting on the substrate, which results in the formation of well-adhered and dense coatings. Clearly, particles in flight conditions, such as velocity, trajectory, temperature, and melting state, have enormous influence on the coating properties and should be well understood to control and improve the coating quality. The focus of this study is on the high velocity oxygen fuel (HVOF spraying and high velocity suspension flame spraying (HVSFS techniques, which are widely used in academia and industry to generate different types of coatings. Extensive numerical and experimental studies were carried out and are still in progress to estimate the particle in-flight behavior in thermal spray processes. In this review paper, the fundamental phenomena involved in the mentioned thermal spray techniques, such as shock diamonds, combustion, primary atomization, secondary atomization, etc., are discussed comprehensively. In addition, the basic aspects and emerging trends in simulation of thermal spray processes are reviewed. The numerical approaches such as Eulerian-Lagrangian and volume of fluid along with their advantages and disadvantages are explained in detail. Furthermore, this article provides a detailed review on simulation studies published to date.

  9. Viscosity of colloidal suspensions

    Energy Technology Data Exchange (ETDEWEB)

    Cohen, E.G.D. [Rockefeller Univ., New York, NY (United States); Schepper, I.M. de [Delft Univ. of Technology (Netherlands)

    1995-12-31

    Simple expressions are given for the effective Newtonian viscosity as a function of concentration as well as for the effective visco-elastic response as a function of concentration and imposed frequency, of monodisperse neutral colloidal suspensions over the entire fluid range. The basic physical mechanisms underlying these formulae are discussed. The agreement with existing experiments is very good.

  10. Electrically actuatable doped polymer flakes and electrically addressable optical devices using suspensions of doped polymer flakes in a fluid host

    Science.gov (United States)

    Trajkovska-Petkoska, Anka; Jacobs, Stephen D.; Marshall, Kenneth L.; Kosc, Tanya Z.

    2010-05-11

    Doped electrically actuatable (electrically addressable or switchable) polymer flakes have enhanced and controllable electric field induced motion by virtue of doping a polymer material that functions as the base flake matrix with either a distribution of insoluble dopant particles or a dopant material that is completely soluble in the base flake matrix. The base flake matrix may be a polymer liquid crystal material, and the dopants generally have higher dielectric permittivity and/or conductivity than the electrically actuatable polymer base flake matrix. The dopant distribution within the base flake matrix may be either homogeneous or non-homogeneous. In the latter case, the non-homogeneous distribution of dopant provides a dielectric permittivity and/or conductivity gradient within the body of the flakes. The dopant can also be a carbon-containing material (either soluble or insoluble in the base flake matrix) that absorbs light so as to reduce the unpolarized scattered light component reflected from the flakes, thereby enhancing the effective intensity of circularly polarized light reflected from the flakes when the flakes are oriented into a light reflecting state. Electro-optic devices contain these doped flakes suspended in a host fluid can be addressed with an applied electric field, thus controlling the orientation of the flakes between a bright reflecting state and a non-reflecting dark state.

  11. Magnesium ferrite nanocrystal clusters for magnetorheological fluid with enhanced sedimentation stability

    Science.gov (United States)

    Wang, Guangshuo; Ma, Yingying; Li, Meixia; Cui, Guohua; Che, Hongwei; Mu, Jingbo; Zhang, Xiaoliang; Tong, Yu; Dong, Xufeng

    2017-01-01

    In this study, magnesium ferrite (MgFe2O4) nanocrystal clusters were synthesized using an ascorbic acid-assistant solvothermal method and evaluated as a candidate for magnetorheological (MR) fluid. The morphology, microstructure and magnetic properties of the MgFe2O4 nanocrystal clusters were investigated in detail by field emission scanning electron microscopy (FESEM), transmission electron microscope (TEM), thermogravimetric analyzer (TGA), X-ray diffraction (XRD) and superconducting quantum interference device (SQUID). The MgFe2O4 nanocrystal clusters were suspended in silicone oil to prepare MR fluid and the MR properties were tested using a Physica MCR301 rheometer fitted with a magneto-rheological module. The prepared MR fluid showed typical Bingham plastic behavior, changing from a liquid-like to a solid-like structure under an external magnetic field. Compared with the conventional carbonyl iron particles, MgFe2O4 nanocrystal clusters-based MR fluid demonstrated enhanced sedimentation stability due to the reduced mismatch in density between the particles and the carrier medium. In summary, the as-prepared MgFe2O4 nanocrystal clusters are regarded as a promising candidate for MR fluid with enhanced sedimentation stability.

  12. Influence of MR damper modeling on vehicle dynamics

    Science.gov (United States)

    de-J Lozoya-Santos, Jorge; Morales-Menendez, Ruben; Ramirez-Mendoza, Ricardo A.; Vivas-Lopez, Carlos A.

    2013-12-01

    The influence of magneto-rheological damper modeling in vehicle dynamics analysis is studied. Several tests using CarSim™ compare a four-corner controlled semi-active suspension for two different magneto-rheological damper models. The magneto-rheological damper characteristics were identified from experimental data. A model-free controller discards the influence of control and emphasizes the compliance of the magneto-rheological damper model; the characteristics of the vehicle index performance considered were comfort, road holding, handling, roll and suspension deflection. The comparison for magneto-rheological damper dynamics and semi-active suspension covers the automotive bandwidth. The results show that high precision of a magneto-rheological damper model as an isolated feature is not enough. The magneto-rheological damper model, as a component of a vehicle suspension, needs to simulate with passive precision and variable damping forces. The findings exhibit the requisite of accurate models for evaluation of semi-active control systems in classic tests. The lack of the friction component in a magneto-rheological damper model leads to an overestimation in handling and stability.

  13. 磁流变半主动空气悬架混合天地棚控制策略研究%Research on the Mixed Sky-hook and Ground-hook Control Strategy Based on Magneto-rheological Semi-active Air Suspension

    Institute of Scientific and Technical Information of China (English)

    江洪; 刘如奎

    2014-01-01

    以磁流变减振器半主动空气悬架为研究对象,基于流体动力学理论建立空气弹簧数学模型,利用试验数据建立磁流变减振器多项式模型.考虑到空气弹簧刚度和磁流变减振器阻尼的非线性,将其以空气弹簧和磁流变减振器非线性力的形式引入到四分之一车辆动力学模型中;以汽车行驶平顺性,轮胎接地性和操纵稳定性的综合性能为控制目标,利用加权系数u引入混合天地棚控制策略,并分析了不同的u值对悬架各性能指标的影响,当u取0.8时,悬架综合性能最好,簧上质量加速度均方根值改善达23.2%,轮胎动载荷均方根值降低17.4%,悬架动行程略有改善.

  14. Effect of MR Fluid Damping during Milling of CFRP Laminates

    Directory of Open Access Journals (Sweden)

    Hakeemuddin Ahmed

    2016-06-01

    Full Text Available Machining of fiber reinforced composites is an essential activity taken up in order to integrate them with other components. Carbon fiber reinforced polymer (CFRP composites are difficult to machine owing to the nonhomogeneity of their constituent materials and abrasive nature. As these materials involve more than one phase, the variation of cutting forces is rather large, which leads to tool chatter and poor surface finish. Therefore the proper selection of the tool, process parameters and the ability to control the machining forces would result in better tolerances and improved surface finish. In this study, multiple slots are machined in CFRP laminates under different machining conditions of spindle speed, feed and depth of cut. A comparative study is made by conducting the same set of experiments under the influence of the magneto- rheological (MR damping in order to assess the tool deflection. It is observed that the MR fluid damping reduces the tool deflection and thus improves the quality of machined surfaces.

  15. Analysis and design of device using electrorheological/magnetorheological fluid with variable stiffness

    Science.gov (United States)

    Jin, Dejiang; Chen, Jiaqi; Huang, Jun

    1998-01-01

    According to the properties of Electro-Rheological/Magneto- Rheological Fluid (ER/MR fluid), a device whose stiffness can be adjusted by electric field and/or magnetic field was designed. The basic mechanical properties were analyzed theoretically. The relation of resistance of piston movement to sped of piston movement is discussed, especially asymptotically relation of slow moving and to fast moving was given. And the basic mechanical properties was tested actually. The stiffness of element combined a device with a spring was characterized with accumulation of energy of the unit in vibration. And then the character of stiffness change of the device element with change of yield stress of ER/MR fluid was discussed. The method of optimizing parameters to improve control capability for some condition was discussed. The results indicate that the device is an effective controllable stiffness element. For a controllable stiffness element, its best working state is that its critical resistance is nearly equal to vibration force. For the device used for high frequency, the duct with a larger width and gap is recommended. But for the device demanding large critical force, as used in civil engineering, the duct with larger length and smaller gap is recommended.

  16. 磁流变液矩形夹层板的动力特性分析%Dynamics Analysis of Rectangular Sandwich Plates with Magnetorheological Fluid

    Institute of Scientific and Technical Information of China (English)

    张冲; 鲁刘磊

    2013-01-01

      作为一种新型智能材料,磁流变液的应用研究近年来倍受重视。从磁流变液的特性出发,对含磁流变液矩形夹层板结构的动力特性进行了研究。在经典的夹层板理论基础上,利用能量法建立了含磁流变液矩形夹层板结构的运动微分方程,导出了四边简支条件下的磁流变液矩形夹层板的固有频率和损耗因子的解析表达式。通过算例,分析了不同磁场强度对磁流变液矩形夹层板的固有频率和损耗因子的影响,并与有限元分析计算的结果进行了比较,两者结果吻合较好。分析和计算结果表明:随着外加磁场强度的增加,夹层板的固有频率和损耗因子均增大,说明磁流变液在外加磁场作用下对夹层板有明显的抑振作用。%As a kind of new intelligent materials, the application of magneto rheological fluid (MRF) has been paid much attention in recent years. According to the characteristics of MR fluid, this paper focuses on dynamics analysis of a rectangular sandwich plate with magneto-rheological fluid. Based on the classical laminated plate theory, the differential equation of motion of rectangular sandwich plate with magnet- rheological fluid is established by the Energy Method, and the analytical expression of the natural frequency and energy loss factor of the rectangular sandwich plate with simply supported on four sides is obtained. Moreover, through a specific example, this paper analyzes the influence of different magnetic field intensity on the natural frequency and loss factor of magnetic-rheological fluid rectangular sandwich plate, and the result is compared with that obtained by finite element analysis. Both results have good agreement. Both the natural frequency and loss factor of sandwich plate increase with increasing of the strength of the applied magnetic field. The results show that magneto-rheological fluid has a significant effect on vibration suppression

  17. Study on fuzzy control of front suspension with MRD of mine articulated dump truck%基于磁流变液阻尼器的矿用铰接式自卸车前悬架模糊控制研究

    Institute of Scientific and Technical Information of China (English)

    田朝阳; 孟克明; 郭志军; 李忠利; 吴静波

    2013-01-01

    The model of a semi-active suspension with MRD (Magneto-Rheological Damper) of minearticulated dump truck was set up to explore the high-efficient vibration control of this kind of suspension.A double-input and single-output fuzzy control system of the suspension was designed,and its simulation model was built by Fuzzy Logic Toolbox of MATLAB.In addition,simulation of the semi-active suspension under random road excitation was conducted by using Simulink.After studying the variation laws of such four parameters as vertical acceleration of suspended mass,angular acceleration of suspended mass,suspension dynamic deflection and tire dynamic load,it was concluded that the fuzzy control of the semi-active suspension could effective improve the ride comfort of the mine articulated dump truck.%通过建立一种基于磁流变液阻尼器的半主动矿用自卸车前悬架模型,来探索该类悬架的高效振动控制方法.设计了一种双输入单输出的悬架模糊控制器,并利用MATLAB模糊控制工具箱建立了其仿真模型.利用Simufink对半主动悬架在随机路面激励下进行仿真计算.通过研究悬挂质量垂向加速度、悬挂质量角加速度、悬架动挠度和轮胎动载4个参数的变化规律,发现模糊控制半主动悬架可有效改善矿用铰接式自卸车的平顺性和乘坐舒适性.

  18. EDITORIAL: Colloidal suspensions Colloidal suspensions

    Science.gov (United States)

    Petukhov, Andrei; Kegel, Willem; van Duijneveldt, Jeroen

    2011-05-01

    Special issue in honour of Henk Lekkerkerker's 65th birthday Professor Henk N W Lekkerkerker is a world-leading authority in the field of experimental and theoretical soft condensed matter. On the occasion of his 65th birthday in the summer of 2011, this special issue celebrates his many contributions to science. Henk Lekkerkerker obtained his undergraduate degree in chemistry at the University of Utrecht (1968) and moved to Calgary where he received his PhD in 1971. He moved to Brussels as a NATO fellow at the Université Libre de Bruxelles and was appointed to an assistant professorship (1974), an associate professorship (1977) and a full professorship (1980) in physical chemistry at the Vrije Universiteit Brussel. In 1985 he returned to The Netherlands to take up a professorship at the Van 't Hoff Laboratory, where he has been ever since. He has received a series of awards during his career, including the Onsager Medal (1999) of the University of Trondheim, the Bakhuys Roozeboom Gold Medal (2003) of the Royal Dutch Academy of Arts and Sciences (KNAW), the ECIS-Rhodia European Colloid and Interface Prize (2003), and the Liquid Matter Prize of the European Physical Society (2008). He was elected a member of KNAW in 1996, was awarded an Academy Chair position in 2005, and has held several visiting lectureships. Henk's work focuses on phase transitions in soft condensed matter, and he has made seminal contributions to both the theoretical and experimental aspects of this field. Here we highlight three major themes running through his work, and a few selected publications. So-called depletion interactions may lead to phase separation in colloid-polymer mixtures, and Henk realised that the partitioning of polymer needs to be taken into account to describe the phase behaviour correctly [1]. Colloidal suspensions can be used as model fluids, with the time- and length-scales involved leading to novel opportunities, notably the direct observation of capillary waves at a

  19. Vibration analysis and optimal design of multi-layer plates partially treated with the MR fluid

    Science.gov (United States)

    Eshaghi, Mehdi; Sedaghati, Ramin; Rakheja, Subhash

    2017-01-01

    The vibration characteristics of a sandwich plate partially treated with the Magneto-Rheological (MR) fluid are investigated numerically and experimentally considering different boundary conditions and intensities of the magnetic flux. A cantilevered sandwich plate consisting of an aluminum host layer with nine equal cavities for the MR fluid treatments and a constraining layer was fabricated for experimental characterizations and validations of the finite-element (FE) model. The dynamic responses of the untreated plate and the partially treated plate, where only one of the nine cavities in the core layer was filled with the MR fluid (MRF 132DG), were measured under harmonic excitation applied at the fixed support. The finite element model of the sandwich plate, developed using the classical plate theory (CPT) and first-order shear deformation theory (FSDT) is verified using the experimental data. The FE model considers the effect of slippage between the top and bottom layers of the structure. The validated FE model is subsequently used to investigate the effects of partial MR fluid treatments, magnetic flux intensity and boundary conditions on the dynamic response characteristics of the structure. The effect of shear deformation on the vibration properties of the MR sandwich plate is further highlighted. Finally, three optimization problems are formulated to identify optimal locations for the MR fluid treatments so as to maximize the variations in the natural frequencies and damping ratios in response to magnetic field. The solution of the optimization problem, attained using the genetic algorithm (GA) suggested that the MR fluid applied to locations with noticeable shear strain can maximize the stiffness variations and damping of the structure, significantly.

  20. Dense Suspension Splash

    Science.gov (United States)

    Zhang, Wendy; Dodge, Kevin M.; Peters, Ivo R.; Ellowitz, Jake; Klein Schaarsberg, Martin H.; Jaeger, Heinrich M.

    2014-03-01

    Upon impact onto a solid surface at several meters-per-second, a dense suspension plug splashes by ejecting liquid-coated particles. We study the mechanism for splash formation using experiments and a numerical model. In the model, the dense suspension is idealized as a collection of cohesionless, rigid grains with finite surface roughness. The grains also experience lubrication drag as they approach, collide inelastically and rebound away from each other. Simulations using this model reproduce the measured momentum distribution of ejected particles. They also provide direct evidence supporting the conclusion from earlier experiments that inelastic collisions, rather than viscous drag, dominate when the suspension contains macroscopic particles immersed in a low-viscosity solvent such as water. Finally, the simulations reveal two distinct routes for splash formation: a particle can be ejected by a single high momentum-change collision. More surprisingly, a succession of small momentum-change collisions can accumulate to eject a particle outwards. Supported by NSF through its MRSEC program (DMR-0820054) and fluid dynamics program (CBET-1336489).

  1. The Rheology of Concentrated Suspensions

    Energy Technology Data Exchange (ETDEWEB)

    Andreas Acrivos

    2004-09-07

    Research program on the rheological properties of flowing suspensions. The primary purpose of the research supported by this grant was to study the flow characteristics of concentrated suspensions of non-colloidal solid particles and thereby construct a comprehensive and robust theoretical framework for modeling such systems quantitatively. At first glance, this seemed like a modest goal, not difficult to achieve, given that such suspensions were viewed simply as Newtonian fluids with an effective viscosity equal to the product of the viscosity of the suspending fluid times a function of the particle volume fraction. But thanks to the research findings of the Principal Investigator and of his Associates, made possible by the steady and continuous support which the PI received from the DOE Office of Basic Energy Sciences, the subject is now seen to be more complicated and therefore much more interesting in that concentrated suspensions have been shown to exhibit fascinating and unique rheological properties of their own that have no counterpart in flowing Newtonian or even non-Newtonian (polymeric) fluids. In fact, it is generally acknowledged that, as the result of these investigations for which the PI received the 2001 National Medal of Science, our understanding of how suspensions behave under flow is far more detailed and comprehensive than was the case even as recently as a decade ago. Thus, given that the flow of suspensions plays a crucial role in many diverse physical processes, our work has had a major and lasting impact in a subject having both fundamental as well as practical importance.

  2. Modeling of curvilinear suspension flows

    Science.gov (United States)

    Morris, Jeffrey F.; Boulay, Fabienne

    1996-11-01

    The curvilinear parallel-plate and cone-and-plate rheometric flows of monodisperse noncolloidal suspensions have been modeled. Although nonuniform in shear rate, dotγ, the parallel-plate flow has been shown experimentally(A. W. Chow, S. W. Sinton, J. H. Iwayima & T. S. Stephens 1994 Phys. Fluids) 6, 2561. not to exhibit particle migration, contrary to predictions of prior suspension-flow modeling. Predictions of nonuniform particle volume fraction, φ, by the suspension-balance model(P. R. Nott & J. F. Brady 1994 J. Fluid Mech.) 275, 157. for parallel-plate and cone-and-plate flow without normal stress differences are presented. The ``nonmigration'' in parallel-plate flow may be attributed to bulk suspension normal stress differences: assuming the bulk stress has the form Σ ~ η dotγ Q(φ) with η the fluid viscosity, nonmigration is predicted for parallel-plate flow provided that Q_33 = (1/2) Q_11 at the bulk φ of interest, with 1 the flow direction and 3 the vorticity direction. Extending the model to include normal stress differences satisfying this requirement, a range of migration behavior is predicted for the cone-and-plate flow depending upon the ratio Q_11/Q_22.

  3. Interplay of micro-scale flow and fluid micro/nanostructure: Solutions of DNA and suspensions of single walled carbon nanotubes

    Science.gov (United States)

    Duggal, Rajat

    The dynamics of dilute solutions of DNA flowing in a scaled clown roll-knife free surface coating flow are investigated on multiple scales. The flow is generated between a rotating roll and a stationary glass knife. Extension of fluorescently stained DNA molecules is measured at the minimum gap at low roll speeds. The macroscopic flow is computed and microscopic predictions are obtained by simulating the DNA by Brownian dynamics combined with successive fine-graining (Sunthar and Ravi Prakash 2005). The simulations predict that the DNA should stretch almost to full extension near the roll surface in the region of minimum gap; this does not agree with experimental measurements. The assumption of linear velocity across the chains fails near free surfaces and is the likely cause of the discrepancy. At high roll speed two separation surfaces arise in the coating bead. The distribution of DNA extension is measured at the separation surface upstream of minimum gap. Slow nodular recirculations are present under the upstream and downstream free surfaces; unexpectedly, DNA molecules are stretched axially in these regions. Individual single-walled carbon nanotubes (SWNTs) in aqueous suspension are visualized directly by fluorescence video-microscopy. The fluorescent tagging is simple, biocompatible, and allows observation of the dynamics of SWNTs in water. The rotational diffusion coefficient in confinement is measured and the critical concentration at which SWNTs in suspensions start interacting is determined. By analyzing the fluctuating shape of SWNTs, the persistence length of SWNTs is found to range between 32 and 174 mum, in agreement with theoretical estimates; thus, common SWNTs in liquids can be considered as rigid Brownian rods in the absence of imposed external fields. Drying microscopic drops of a suspension of individual SWNTs in aqueous solution of F68 pluronic surfactant exhibit complex dynamics. The drops dry on glass substrates forming a "crust" at the free

  4. Conditioning out-of-date bank-stored red blood cells using a cell-saver auto-transfusion device: effects on numbers of red cells and quality of suspension fluid.

    Science.gov (United States)

    Read, M S; Coles, P; Pomeroy, M; Anderson, E; Aziz, M I

    2014-11-01

    We investigated the utility of a cell-saver device for processing out-of-date red blood cells, by washing twenty bags of red blood cells that had been stored for between 36 and 55 days. The volume of recovered cells, and the characteristics of the suspension fluid, were measured before and after treatment. The ratio of free haemoglobin to total haemoglobin was up to 0.02 before processing, and up to 0.011 afterwards, changing by between -0.013 and +0.003. This ratio met the current standard for free haemoglobin (less than 0.008 in more than 75% of samples), both before and after processing. Ninety-three percent of red blood cells survived the process. Potassium ion concentration fell from above 15 mmol.l(-1) in all cases, to a mean of 6.4 mmol.l(-1) (p red blood cells remained intact after conditioning using a cell-saver, and the process lowered concentrations of potentially toxic solutes in the fluid in which they were suspended.

  5. X-ray Mapping of Dynamic Suspensions

    Science.gov (United States)

    Gholami, Mohammad; Lenoir, Nicolas; Ovarlez, Guillaume; Hormozi, Sarah

    2016-11-01

    Dense non-colloidal suspensions are materials with broad application both in industrial processes and natural phenomena. In most of these applications, the suspensions are either far from equilibrium or strongly non-Newtonian (i.e., non-colloidal particles are suspended in non-Newtonian fluid) meaning that the flow kinetics are not only strain-dependent but also strain-rate dependent. Therefore, experimental techniques must be developed to analyze the flows of these complex suspensions over a wide range of steady and transient shear rates. Techniques such as Nuclear Magnetic Resonance/Imaging (NMR/I) are inapplicable due to low sampling frequency and low image resolution (typically 10 minutes per averaged NMR image of 1x1cm). We introduce a new technique using an X-ray/CT-scan system to study dynamic suspensions. We show our recent results on the application of this technique for the study of shear induced migration of particles in a yield stress matrix fluid in a wide-gap cylindrical Couette cell. This work opens new avenues to study dynamic non-colloidal suspensions and the suspensions with other types of nonlinear suspending fluids such as viscoelastic and shear thickening fluids. NFS(CBET-1554044-CAREER).

  6. Transient response of sheared magnetic powder excited by a stepwise magnetic field and its comparison with ER and MR fluids

    Science.gov (United States)

    Chen, KaiKai; Tian, Yu; Shan, Lei; Jiang, Jile

    2013-09-01

    The transient shear behavior of magnetic powder (MP) excited by a stepwise magnetic field in a rotational magnetic powder clutch (MPC) was experimentally studied. The experiment showed that the stable shear stress was approximately proportional to the applied magnetic flux density. The characteristic rising time of the shear stress was independent of the strength of the magnetic field and was affected by the shear rate. It took less than 0.1 s for the shear stress to rise to 63% (1 - e-1) of the stable value. The transient shear stress rising process consisted of two subprocesses: the chain forming process which was less than 100 ms, and the chain coarsening process lasting for dozens of seconds. Upon switching the field off, the shear stress fell rapidly to zero in 0.1 s. Control methods to improve the transient response time of the MPC were discussed and experimentally verified: applying a low voltage in advance; applying a high level voltage for the torque to rise to the target torque and then a desired voltage. These transient characteristics of MP were compared with those of electrorheological (ER) and magneto-rheological (MR) fluids and actuators. The study provides a better understanding of MP excited by a magnetic field and the implications for application.

  7. Rheological study of an hydrate slurry as secondary two-phase refrigerant. Experimental results and modelling; Etude rheologique d'une suspension d'hydrates en tant que fluide frigoporteur diphasique: resultats experimentaux et modelisation

    Energy Technology Data Exchange (ETDEWEB)

    Darbouret, M.

    2005-12-15

    Secondary two-phase fluids are suspensions of solid crystals. Thanks to the melting latent heat, they present a great interest for cold transportation. Moreover, they are a mean of reducing the amount of classical refrigerant. In the refrigeration field, ice slurries are already used. The goal is now to extend this technology to other temperature ranges suitable for other applications like freezing or air-conditioning. For an air-conditioning application, a TBAB (Tetra-Butyl-Ammonium Bromide) aqueous solution is studied. Under atmospheric pressure and for positive temperatures, this solution crystallizes into ice-like compounds named 'hydrates'. First, the physical properties of the aqueous solution and its crystallisation conditions were studied. Two different types of hydrates can appear. The goal of the experimental set-up is to study the rheological behaviour of two-phase fluids. Slurries are made in brushed-surface heat exchanger and pumped into pipes where flow rates and pressure drops are measured. The rheological behaviour of TBAB hydrates slurries can be described using a Bingham fluid model. We highlight that the two rheological parameters, which are the apparent viscosity and the yield shear stress, depend on the volume fraction of crystal of course, but also on the hydrate type, and on the initial concentration of the solution. The yield shear stress is interpreted as the consequence of the Van der Waals inter-particle interaction forces. Finally, possible stratification effects are modelled with a finite difference method. The principle is to calculate particle concentration and velocity profiles following the flow of the slurry. Calculations are validated with experimental velocity profiles published by P. Reghem (2002). This model underlines the influence of the particle distribution in the pipe on pressure drops. (author)

  8. Shear Thinning of Noncolloidal Suspensions

    Science.gov (United States)

    Vázquez-Quesada, Adolfo; Tanner, Roger I.; Ellero, Marco

    2016-09-01

    Shear thinning—a reduction in suspension viscosity with increasing shear rates—is understood to arise in colloidal systems from a decrease in the relative contribution of entropic forces. The shear-thinning phenomenon has also been often reported in experiments with noncolloidal systems at high volume fractions. However its origin is an open theoretical question and the behavior is difficult to reproduce in numerical simulations where shear thickening is typically observed instead. In this letter we propose a non-Newtonian model of interparticle lubrication forces to explain shear thinning in noncolloidal suspensions. We show that hidden shear-thinning effects of the suspending medium, which occur at shear rates orders of magnitude larger than the range investigated experimentally, lead to significant shear thinning of the overall suspension at much smaller shear rates. At high particle volume fractions the local shear rates experienced by the fluid situated in the narrow gaps between particles are much larger than the averaged shear rate of the whole suspension. This allows the suspending medium to probe its high-shear non-Newtonian regime and it means that the matrix fluid rheology must be considered over a wide range of shear rates.

  9. 金属核心 /高聚物膜复合悬浮相电流变流体材料%Metal Core/Polymer Coating Compounded Suspension for Electrorheologic Fluid

    Institute of Scientific and Technical Information of China (English)

    丁文; 范志康; 徐传骧; 卢凤纪

    2001-01-01

    Aiming at researching and developing new compounded suspensions to sever as electrorheological fluid (ERF), a metal core/polymer coating compounded suspension for ERF has been designed according to the principle of media polarization. Based on this evolution,a series of metal core/high polymer coating compounded particles such as Zn/poly-styrene-butyl-acrylate compounded particles, Ni/poly-styrene-butyl-acrylate compounded particles, Ni/polystyrene compounded particles, Zn/polystyrene compounded particles have been prepared adopting the emulsion polymerization together with the micro-encapsulation techniques as well as the acid-alkali matching theory which was initially suggested by Fowkes(schematically depicted in Fig.1). The micro-morphologies of these compounded particles were measured using scan electron microscophy(the SEM photography of Fig.2 exhibits the coated condition of these particles) and the ERF performance of these compounded particles have alse been carried out. The performance test results indicate that the mechanical properties (refer to Fig.5~ 10 ) and the stability of ERF were improved, i.e. shear strength was no less than 2 kPa and segregation resistance was intensified significantly compared with that of metal core, which shows that these materials are promising for acting as ERF though further modification should be necessary. Besides, from the performance test results it is apparently found that different compounded suspensions made up of different metal cores or polymer coatings possess various mechanical properties,and explanations for this phenomenon will discussed in detail elsewhere.%针对电流变流体悬浮相材料的开发与研究,根据介质极化原理,设计开发了金属核心 /高聚物膜复合悬浮相电流变流体材料,在乳液聚合与微胶囊包覆技术的基础上,制备出了金属核心 /高聚物膜复合颗粒 .并对这种金属核心 /高聚物膜复合颗粒的电流变流体

  10. Heat and mass transfer in particulate suspensions

    CERN Document Server

    Michaelides, Efstathios E (Stathis)

    2013-01-01

    Heat and Mass Transfer in Particulate Suspensions is a critical review of the subject of heat and mass transfer related to particulate Suspensions, which include both fluid-particles and fluid-droplet Suspensions. Fundamentals, recent advances and industrial applications are examined. The subject of particulate heat and mass transfer is currently driven by two significant applications: energy transformations –primarily combustion – and heat transfer equipment. The first includes particle and droplet combustion processes in engineering Suspensions as diverse as the Fluidized Bed Reactors (FBR’s) and Internal Combustion Engines (ICE’s). On the heat transfer side, cooling with nanofluids, which include nanoparticles, has attracted a great deal of attention in the last decade both from the fundamental and the applied side and has produced several scientific publications. A monograph that combines the fundamentals of heat transfer with particulates as well as the modern applications of the subject would be...

  11. Restructuring and aging in a capillary suspension.

    Science.gov (United States)

    Koos, Erin; Kannowade, Wolfgang; Willenbacher, Norbert

    2014-12-01

    The rheological properties of capillary suspensions, suspensions with small amounts of an added immiscible fluid, are dramatically altered with the addition of the secondary fluid. We investigate a capillary suspension to determine how the network ages and restructures at rest and under applied external shear deformation. The present work uses calcium carbonate suspended in silicone oil (11 % solids) with added water as a model system. Aging of capillary suspensions and their response to applied oscillatory shear is distinctly different from particulate gels dominated by the van der Waals forces. The suspensions dominated by the capillary force are very sensitive to oscillatory flow, with the linear viscoelastic regime ending at a deformation of only 0.1% and demonstrating power-law aging behavior. This aging persists for long times at low deformations or for shorter times with a sudden decrease in the strength at higher deformations. This aging behavior suggests that the network is able to rearrange and even rupture. This same sensitivity is not demonstrated in shear flow where very high shear rates are required to rupture the agglomerates returning the apparent viscosity of capillary suspensions to the same viscosity as for the pure vdW suspension. A transitional region is also present at intermediate water contents wherein the material response depends very strongly on the type, strength, and duration of the external forcing.

  12. Crew Health And Recreation Gear Exercise Device Project

    Data.gov (United States)

    National Aeronautics and Space Administration — A magneto-Rheological (MR) fluid based exoskeleton leg demonstrator was developed to help long duration exploration mission crews obtain exercise with entertainment...

  13. Variable stiffness and damping suspension system for train

    Science.gov (United States)

    Sun, Shuaishuai; Deng, Huaxia; Li, Weihua

    2014-03-01

    As the vibration of high speed train becomes fierce when the train runs at high speed, it is crucial to develop a novel suspension system to negotiate train's vibration. This paper presents a novel suspension based on Magnetorheological fluid (MRF) damper and MRF based smart air spring. The MRF damper is used to generate variable damping while the smart air spring is used to generate field-dependent stiffness. In this paper, the two kind smart devices, MRF dampers and smart air spring, are developed firstly. Then the dynamic performances of these two devices are tested by MTS. Based on the testing results, the two devices are equipped to a high speed train which is built in ADAMS. The skyhook control algorithm is employed to control the novel suspension. In order to compare the vibration suppression capability of the novel suspension with other kind suspensions, three other different suspension systems are also considered and simulated in this paper. The other three kind suspensions are variable damping with fixed stiffness suspension, variable stiffness with fixed damping suspension and passive suspension. The simulation results indicate that the variable damping and stiffness suspension suppresses the vibration of high speed train better than the other three suspension systems.

  14. Modeling and test of a kinaesthetic actuator based on MR fluid for haptic applications.

    Science.gov (United States)

    Yang, Tae-Heon; Koo, Jeong-Hoi; Kim, Sang-Youn; Kwon, Dong-Soo

    2017-03-01

    Haptic display units have been widely used for conveying button sensations to users, primarily employing vibrotactile actuators. However, the human feeling for pressing buttons mainly relies on kinaesthetic sensations (rather than vibrotactile sensations), and little studies exist on small-scale kinaesthetic haptic units. Thus, the primary goals of this paper are to design a miniature kinaesthetic actuator based on Magneto-Rheological (MR) fluid that can convey various button-clicking sensations and to experimentally evaluate its haptic performance. The design focuses of the proposed actuator were to produce sufficiently large actuation forces (resistive forces) for human users in a given size constraint and to offer a wide range of actuation forces for conveying vivid haptic sensations to users. To this end, this study first performed a series of parametric studies using mathematical force models for multiple operating modes of MR fluid in conjunction with finite element electromagnetism analysis. After selecting design parameters based on parametric studies, a prototype actuator was constructed, and its performance was evaluated using a dynamic mechanical analyzer. It measured the actuator's resistive force with a varying stroke (pressed depth) up to 1 mm and a varying input current from 0 A to 200 mA. The results show that the proposed actuator creates a wide range of resistive forces from around 2 N (off-state) to over 9.5 N at 200 mA. In order to assess the prototype's performance in the terms of the haptic application prospective, a maximum force rate was calculated to determine just noticeable difference in force changes for the 1 mm stoke of the actuator. The results show that the force rate is sufficient to mimic various levels of button sensations, indicating that the proposed kinaesthetic actuator can offer a wide range of resistive force changes that can be conveyed to human operators.

  15. Suspension flow modelling in particle migration and microfiltration

    NARCIS (Netherlands)

    Vollebregt, H.M.; Sman, van der R.G.M.; Boom, R.M.

    2010-01-01

    We review existing mixture models for shear-induced migration (SIM) in flowing viscous, concentrated particle suspensions via an analysis of the models from the perspective of a two-fluid formulation. Our analysis shows that particle suspensions in strong non-linear shear fields are a prime example

  16. Urinary incontinence - retropubic suspension

    Science.gov (United States)

    ... Marchetti-Krantz (MMK) procedure; Laparoscopic retropubic colposuspension; Needle suspension; Burch colposuspension ... bladder. There are two ways to do retropubic suspension: open surgery or laparoscopic surgery. Either way, surgery ...

  17. Suspension Trauma / Orthostatic Intolerance

    Science.gov (United States)

    ... of Science and Technology Assessment Printer Friendly Version Suspension Trauma/Orthostatic Intolerance Safety and Health Information Bulletin ... information about the hazards of orthostatic intolerance and suspension trauma when using fall arrest systems. This bulletin: ...

  18. Collapsing granular suspensions

    OpenAIRE

    Kadau, D.; Andrade Jr, J. S.; Herrmann, H. J.

    2009-01-01

    A 2D contact dynamics model is proposed as a microscopic description of a collapsing suspension/soil to capture the essential physical processes underlying the dynamics of generation and collapse of the system. Our physical model is compared with real data obtained from in situ measurements performed with a natural collapsing/suspension soil. We show that the shear strength behavior of our collapsing suspension/soil model is very similar to the behavior of this collapsing suspension soil, for...

  19. A New Angle on Microscopic Suspension Feeders near Boundaries

    OpenAIRE

    Pepper, Rachel E.; Roper, Marcus; Ryu, Sangjin; Matsumoto, Nobuyoshi; Nagai, Moeto; Stone, Howard A.

    2013-01-01

    Microscopic sessile suspension feeders are a critical component in aquatic ecosystems, acting as an intermediate trophic stage between bacteria and higher eukaryotic taxa. Because they live attached to boundaries, it has long been thought that recirculation of the feeding currents produced by sessile suspension feeders inhibits their ability to access fresh fluid. However, previous models for the feeding flows of these organisms assume that they feed by pushing fluid perpendicular to surfaces...

  20. A new angle on microscopic suspension feeders near boundaries.

    Science.gov (United States)

    Pepper, Rachel E; Roper, Marcus; Ryu, Sangjin; Matsumoto, Nobuyoshi; Nagai, Moeto; Stone, Howard A

    2013-10-15

    Microscopic sessile suspension feeders are a critical component in aquatic ecosystems, acting as an intermediate trophic stage between bacteria and higher eukaryotic taxa. Because they live attached to boundaries, it has long been thought that recirculation of the feeding currents produced by sessile suspension feeders inhibits their ability to access fresh fluid. However, previous models for the feeding flows of these organisms assume that they feed by pushing fluid perpendicular to surfaces they live upon, whereas we observe that sessile suspension feeders often feed at an angle to these boundaries. Using experiments and calculations, we show that living suspension feeders (Vorticella) likely actively regulate the angle that they feed relative to a substratum. We then use theory and simulations to show that angled feeding increases nutrient and particle uptake by reducing the reprocessing of depleted water. This work resolves an open question of how a key class of suspension-feeding organisms escapes physical limitations associated with their sessile lifestyle.

  1. Gravity filtration of suspensions: permeability effects

    Science.gov (United States)

    Soori, Tejaswi; Wang, Mengyu; Ward, Thomas

    2015-11-01

    This paper examines the filtration rates of mono-modal suspensions as a function of time and a cake layer builds up through theory and experimentation. Darcy's Law, which describes fluid flow through porous media, was applied along with the Kynch theory of sedimentation, which provides the basis for analyzing low concentration (ϕ filter media. A CCD camera was used to capture images of the cake formation and fluid drainage processes, and subsequent image and theoretical analysis found the fluid flow experienced a constant pressure loss due to the permeability of the filter media, whereas the experienced pressure loss due to the cake formation varies as a function of time, ϕ and d. The rate of cake formation was also found to be independent of ϕ but dependent on d which can be attributed to a change in porosity affecting permeability. Studies on similar systems with multi-modal suspensions are in-progress.

  2. Relationship Between the Shape of Suspension Particle and Ground State Structure of Electrorheological Solid

    Institute of Scientific and Technical Information of China (English)

    WU Feng; HE Pei; CHEN Zu-Yao; JIANG Wan-Quan

    2000-01-01

    The effect of the shape of suspension particle in electrorheological (ER) fluid on the ground state structure of ER solid is discussed. The results of computation show that the ground state structure will change with the shape of suspension particle. This phenomenon is a kind of phase transitions that takes the shape factors of suspension particle as tuning parameters. The variation-value of interaction energy of the lattice structure of ER solid with the shape factors of suspension particle is sometimes noticeable.

  3. Dissipative Particle Dynamics simulation of colloidal suspensions

    Science.gov (United States)

    Jamali, Safa; Boromand, Arman; Maia, Joao

    2014-03-01

    DPD as a mesoscale method was firstly proposed to study dynamics of suspensions under flow condition. However the proposed method failed to capture shear properties of suspensions because it lacked: first a potential to reproduce lubrication forces and second a clear definition for the colloid surface. Recently we reported a modified DPD method which defines colloidal particles as particles with hard core and a dissipative coat. An additional lubrication force was introduced to include the short-range hydrodynamics that are not captured in original DPD. The model was found to be able to reproduce shear properties of suspensions for a wide range of different systems, from monodisperse to bimodal with different volume fractions, compositions and size ratios. In present work our modified DPD method is employed to study both equilibrium and flow properties of colloidal suspension. Zero shear viscosity of suspension is measured using Green-Kubo expressions and the results are compared to theoretical predictions. Furthermore, structure formation in suspensions is studied in respect to energy landscape of the fluid both at rest and under flow.

  4. Turning bacteria suspensions into a "superfluid"

    CERN Document Server

    López, Héctor Matías; Douarche, Carine; Auradou, Harold; Clément, Eric

    2015-01-01

    The rheological response under simple shear of an active suspension of Escherichia coli is determined in a large range of shear rates and concentrations. The effective viscosity and the time scales characterizing the bacterial organization under shear are obtained. In the dilute regime, we bring evidences for a low shear Newtonian plateau characterized by a shear viscosity decreasing with concentration. In the semi-dilute regime, for particularly active bacteria, the suspension display a "super-fluid" like transition where the viscous resistance to shear vanishes, thus showing that macroscopically, the activity of pusher swimmers organized by shear, is able to fully overcome the dissipative effects due to viscous loss.

  5. Magneto-rheological elastomer (MRE) based composite structures for micro-vibration control

    Institute of Scientific and Technical Information of China (English)

    YQ Ni; ZG Ying; ZH Chen

    2010-01-01

    Magneto-theological elastomers (MREs) are used to construct composite structures for micro-vibration control of equipment under stochastic support-motion excitations. The dynamic behavior of MREs as a smart viscoelastic material is characterized by a complex modulus dependent on vibration frequency and controllable by external magnetic fields. Frequency-domain solution methods for stochastic micro-vibration response analysis of the MRE-based structural systems are developed to derive the system frequency-response function matrices and the expressions of the velocity response spectrum. With these equations, the root-mean-square (RMS) velocity responses in terms of the one-third octave frequency band spectrum can be calculated. Further, the optimization problem of the complex moduli of the MRE cores is defined by minimizing the velocity response spectra and the RMS velocity responses through altering the applied magnetic fields. Simulation results illustrate the influences of MRE parameters on the RMS velocity responses and the high response reduction capacities of the MRE-hased structures. In addition, the developed frequency-domain analysis methods are applicable to sandwich beam structures with arbitrary cores characterized by complex shear moduli under stochastic excitations described by power spectral density functions, and are valid for a wide frequency range.

  6. Enriched Imperialist Competitive Algorithm for system identification of magneto-rheological dampers

    Science.gov (United States)

    Talatahari, Siamak; Rahbari, Nima Mohajer

    2015-10-01

    In the current research, the imperialist competitive algorithm is dramatically enhanced and a new optimization method dubbed as Enriched Imperialist Competitive Algorithm (EICA) is effectively introduced to deal with high non-linear optimization problems. To conduct a close examination of its functionality and efficacy, the proposed metaheuristic optimization approach is actively employed to sort out the parameter identification of two different types of hysteretic Bouc-Wen models which are simulating the non-linear behavior of MR dampers. Two types of experimental data are used for the optimization problems to minutely examine the robustness of the proposed EICA. The obtained results self-evidently demonstrate the high adaptability of EICA to suitably get to the bottom of such non-linear and hysteretic problems.

  7. Note: Vibration suppression using tunable vibration absorber based on stiffness variable magneto-rheological gel

    Science.gov (United States)

    Shin, Beom-Cheol; Yoon, Jung-Hwan; Kim, Young-Keun; Kim, Kyung-Soo

    2015-10-01

    This paper proposes a novel adaptive tunable vibration absorber (TVA) based on a smart material the magnetorheological gel (MRG) to achieve a wide range of tonal vibration suppression on the primary system to protect any connected sensitive device. The vibration suppression performance of the MRG TVA was analyzed by conducting a modal test of the primary system under different magnetic fields. The experiment verified that the proposed MRG TVA can be controlled to produce 379% of stiffness change or 115% of tuning frequency under just 200 mT magnetic field. The proposed MRG TVA was found to possess a wider tuning frequency range than the TVA based on other smart material such as magnetorheological elastomer.

  8. Semi-active Control of Magneto-Rheological Dampers with Negative Stiffness

    DEFF Research Database (Denmark)

    Bhowmik, Subrata

    2009-01-01

    -rheological (MR) damper is among the most popular and promising devices due to its low power requirement, high dynamic range, high force capacity and robustness. The objective of this paper is to formulate semi -active feedback control methods based on simple linear damper models, which lead to increased damping...

  9. Structure and physical properties of magneto-rheological slurries under perturbation

    OpenAIRE

    De la Calleja, E. M.; J.L. Carrillo; Donado, F.

    2012-01-01

    Dispersions of micrometric magnetic particles in inert liquids acquire a complex multifractal structure when they are exposed to a static magnetic field. If in addition to the static field it is applied on the dispersion an oscillatory magnetic perturbation, the structure formed by the particles, and consequently, some of the physical properties of the system, can be strongly affected. Under certain conditions, by the influence of the perturbation, the structure in the dispersion can be recon...

  10. Collapsing granular suspensions.

    Science.gov (United States)

    Kadau, D; Andrade, J S; Herrmann, H J

    2009-11-01

    A 2D contact dynamics model is proposed as a microscopic description of a collapsing suspension/soil to capture the essential physical processes underlying the dynamics of generation and collapse of the system. Our physical model is compared with real data obtained from in situ measurements performed with a natural collapsing/suspension soil. We show that the shear strength behavior of our collapsing suspension/soil model is very similar to the behavior of this collapsing suspension soil, for both the unperturbed and the perturbed phases of the material.

  11. Numerical homogenization on approach for stokesian suspensions.

    Energy Technology Data Exchange (ETDEWEB)

    Haines, B. M.; Berlyand, L. V.; Karpeev, D. A. (Mathematics and Computer Science); (Department of Mathematics, Pennsylvania State Univ.)

    2012-01-20

    In this technical report we investigate efficient methods for numerical simulation of active suspensions. The prototypical system is a suspension of swimming bacteria in a Newtonian fluid. Rheological and other macroscopic properties of such suspensions can differ dramatically from the same properties of the suspending fluid alone or of suspensions of similar but inactive particles. Elongated bacteria, such as E. coli or B. subtilis, swim along their principal axis, propelling themselves with the help of flagella, attached at the anterior of the organism and pushing it forward in the manner of a propeller. They interact hydrodynamically with the surrounding fluid and, because of their asymmetrical shape, have the propensity to align with the local flow. This, along with the dipolar nature of bacteria (the two forces a bacterium exerts on a fluid - one due to self-propulsion and the other opposing drag - have equal magnitude and point in opposite directions), causes nearby bacteria to tend to align, resulting in a intermittent local ordering on the mesoscopic scale, which is between the microscopic scale of an individual bacterium and the macroscopic scale of the suspension (e.g., its container). The local ordering is sometimes called a collective mode or collective swimming. Thanks to self-propulsion, collective modes inject momentum into the fluid in a coherent way. This enhances the local strain rate without changing the macroscopic stress applied at the boundary of the container. The macroscopic effective viscosity of the suspension is defined roughly as the ratio of the applied stress to the bulk strain rate. If local alignment and therefore local strain-rate enhancement, are significant, the effective viscosity can be appreciably lower than that of the corresponding passive suspension or even of the surrounding fluid alone. Indeed, a sevenfold decrease in the effective viscosity was observed in experiments with B. subtilis. More generally, local collective

  12. Development of Magnetorheological Fluids Based Haptic Display Systems%基于磁流变液的力/触觉再现系统研究进展

    Institute of Scientific and Technical Information of China (English)

    文辞; 宋爱国; 王爱民

    2009-01-01

    力/触觉再现技术是当前新兴的研究领域.介绍了最近10年来基于磁流变液的力/触觉再现系统的国内外研究进展情况.总结了基于磁流变液的力/触觉再现技术的研究内容,包括执行装置的结构设计、模型研究以及再现系统控制研究,讨论了基于磁流变液的力/触觉再现系统开发过程中的关键技术.如提高便携式触觉接口中执行装置的力矩/重量比.减小静态力、克服被动系统力/触觉表达局限性,指出了今后发展的趋势.阐述了基于磁流变液的力/触觉再现系统的优势,并展望了其应用前景.%The haptic display technology is a frontier research area currently. The developments of magneto-rheological fluids based haptic display systems in the last decade are introduced. Magnetorheological fluids based haptic display technique includes actuator design, modeling and display system control, some key issues are discussed, such as a high torque/weight ratio in portable haptie interfaces, a low static force and a limita-tion on presenting haptic of passive type systems. And the developing direction of a magnetorheological fluids based haptic display system in the future is pointed out. Finally the advantages of the system are presented and the application prospect is forecasted.

  13. Electrorheological fluids and methods

    Energy Technology Data Exchange (ETDEWEB)

    Green, Peter F.; McIntyre, Ernest C.

    2015-06-02

    Electrorheological fluids and methods include changes in liquid-like materials that can flow like milk and subsequently form solid-like structures under applied electric fields; e.g., about 1 kV/mm. Such fluids can be used in various ways as smart suspensions, including uses in automotive, defense, and civil engineering applications. Electrorheological fluids and methods include one or more polar molecule substituted polyhedral silsesquioxanes (e.g., sulfonated polyhedral silsesquioxanes) and one or more oils (e.g., silicone oil), where the fluid can be subjected to an electric field.

  14. Seismic response reduction of a three-story building by an MR grease damper

    Science.gov (United States)

    Sakurai, Tomoki; Morishita, Shin

    2017-01-01

    This paper describes an application of magneto- rheological (MR) grease dampers as seismic dampers for a three-story steel structure. MR fluid is widely known as a smart material with rheological properties that can be varied by magnetic field strength. This material has been applied to various types of devices, such as dampers, clutches, and engine mounts. However, the ferromagnetic particles dispersed in MR fluid settle out of the suspension after a certain interval because of the density difference between the particles and their carrier fluid. To overcome this defect, we developed a new type of controllable working fluid using grease as the carrier of magnetic particles. MR grease was introduced into a cylindrical damper, and the seismic performance of the damper was subsequently studied via numerical analysis. The analysis results of the MR grease damper were compared with those of other seismic dampers. We confirmed that the MR grease damper is an effective seismic damper.

  15. Suspension trauma; Le traumatisme de suspension

    Energy Technology Data Exchange (ETDEWEB)

    Trudel, S. [Le Centre de sante et de services sociaux du rocher Perce, Chandler, PQ (Canada)

    2010-07-01

    This presentation discussed the precautions that should be taken to avoid falls from wind turbines or transmission towers. Suspension trauma was explained by a medical doctor in terms of physiology and the body's normal circulation and the elements that disturb normal physiology when in suspension. The trauma occurs following a fall, which carries the risk of 1or more disorders, such as massive hemorrhage, high cardiac pulse, and constriction of blood vessels. Nausea, vertigo, cardiac arrhythmia and sweating occur 15 to 20 minutes following the fall. The presentation emphasized the importance of having qualified personnel at the site and wearing proper harnesses and equipment that supports the neck. figs.

  16. A New Damper for Tracked Vehicle Suspension

    Institute of Scientific and Technical Information of China (English)

    FAN Fu-sheng; LI Meng; XING Zhi; L(U) Jian-gang

    2005-01-01

    The passive suspension system of tracked vehicle is designed to get its suspension parameters based on a certain common velocity and a certain road surface roughness. Its performance optimization only exists in a certain operating mode without far-ranging adaptability. Holding the damper basic frame form and applying semi-active suspension system based on MR (magnetorheological) damper, the vehicle can keep its optimum efficiency between energy dissipation and vibration reduction in all kinds of operating modes. Theoretical analysis and experiments show that the damping performances provided by this MRF(magnetorheological fluids) vane damper are same as those provided by traditional damper, and the new damper has the better controllability and adaptability.

  17. Crust formation in drying colloidal suspensions

    KAUST Repository

    Style, R. W.

    2010-06-30

    During the drying of colloidal suspensions, the desiccation process causes the suspension near the air interface to consolidate into a connected porous matrix or crust. Fluid transport in the porous medium is governed by Darcy\\'s law and the equations of poroelasticity, while the equations of colloid physics govern processes in the suspension. We derive new equations describing this process, including unique boundary conditions coupling the two regions, yielding a moving-boundary model of the concentration and stress profiles during drying. A solution is found for the steady-state growth of a nedimensional crust during constant evaporation rate from the surface. The solution is used to demonstrate the importance of the system boundary conditions on stress profiles and diffusivity in a drying crust. © 2011 The Royal Society.

  18. Research on School Suspension

    Science.gov (United States)

    Iselin, Anne-Marie

    2010-01-01

    Schools across the nation report increases in the use of punitive disciplinary methods (e.g., suspension). The need for these disciplinary practices to address serious student misconduct is undisputed. What research has questioned is why some students seem to be suspended more often than others, what effects suspension has on students, and whether…

  19. Electrical controlled rheology of a suspension of weakly conducting particles in dielectric liquid

    CERN Document Server

    Guegan, Q; Foulc, J N; Tillement, O; Guegan, Quentin

    2006-01-01

    The properties of suspensions of fine particles in dielectric liquid (electrorheological fluids) subjected to an electric field lead to a drastic change of the apparent viscosity of the fluid. For high applied fields (~ 3-5 kV/mm) the suspension congeals to a solid gel (particles fibrillate span the electrode gap) having a finite yield stress. For moderate fields the viscosity of the suspension is continuously controlled by the electric field strength. We have roposed that in DC voltage the field distribution in the solid (particles) and liquid phases of the suspension and so the attractive induced forces between particles and the yield stress of the suspension are controlled by the conductivities of the both materials. In this paper we report investigation and results obtained with nanoelectrorheological suspensions: synthesis of coated nanoparticles (size ~ 50 to 600 nm, materials Gd2O3:Tb, SiOx...), preparation of ER fluids (nanoparticles mixed in silicone oil), electrical and rheological characterization ...

  20. Scattering series in mobility problem for suspensions

    OpenAIRE

    Makuch, Karol

    2012-01-01

    The mobility problem for suspension of spherical particles immersed in an arbitrary flow of a viscous, incompressible fluid is considered in the regime of low Reynolds numbers. The scattering series which appears in the mobility problem is simplified. The simplification relies on the reduction of the number of types of single-particle scattering operators appearing in the scattering series. In our formulation there is only one type of single-particle scattering operator.

  1. Dynamics of Discontinuous Shear Thickening suspensions

    Science.gov (United States)

    Brown, Eric

    2015-03-01

    Concentrated suspensions of hard particles such as cornstarch in water exhibit Discontinuous Shear Thickening, in which an increasing shear rate drives a transition from liquid- to solid-like mechanical behavior. In steady-state shear this phenomena is a result of a dynamic version of jamming in which forces are transmitted along particle contact networks that span to system boundaries and repeatedly form and break up. Several dynamic phenomena observed in such suspensions have long been assumed to be a consequence of this shear thickening, but cannot be explained as a direct result of shear thickening; for example a uniquely strong impact response which allows a person to run on the fluid surface. We perform experiments in which a concentrated suspension is subjected to transient impact. We find that the strong impact response is due a short-lived jammed contact network spanning to the boundaries and a delay time required for this dynamically jammed region to propagate to the boundary. The resulting ability of this system-spanning solid-like region to support loads can explain the ability of a person to run on the surface of these fluids. This delay before a solid-like response may also explain several other dynamic phenomena observed in these fluids.

  2. Rheology of suspensions with aluminum nano-particles

    Directory of Open Access Journals (Sweden)

    Ulrich Teipel

    2009-01-01

    Full Text Available Nano-scale aluminum particles are innovative materials increasingly used in energetic formulations. In this contribution, the rheological behavior of suspensions with either paraffin oil or HTPB as the matrix fluid and nano-scale aluminum (ALEX as the dispersed phase is described and discussed. The paraffin oil/aluminum suspensions exhibit non-Newtonian flow behavior over a wide range of concentrations, whereas the HTPB/aluminum suspensions exhibitNewtonian behavior (i.e. the viscosity is independent of shear stress up to a concentration of 50 vol.% aluminum. Both systems have unusual viscoelastic properties in that their elastic moduli are independent of the solids concentration.

  3. Vibration Control of Vehicle Suspension System by Electrorheological Damper

    Institute of Scientific and Technical Information of China (English)

    ZHAO Xia; ZHANG Yong-fa

    2006-01-01

    An overview of electrorheological (ER) fluid characteristics is given. Based on the Bingham plasticity model and a simple parallel-plate model, the operation principle of ER damper is presented and a four-DOF dynamic model of a vehicle suspension is constructed. Then a semi-active control of vehicle suspension system by ER damper is obtained. According to the semi-active control theory, the acceleration frequency characteristic is achieved with Matlab toolbox. Simulation results show that the vibration of the suspension system is well controlled.

  4. Study on Cell Suspension Culture of Floribunda Rose

    Institute of Scientific and Technical Information of China (English)

    ZHANG Chun'ai; WANG Jingang; FAN Jinping; GONG Shufang; CHE Daidi

    2008-01-01

    Friable callus was induced when immature seeds of floribunda rose were inoculated on MS medium supplemented with 2,4-D 3.0 mg-L-1.When transfered onto subculture media,fi-iable callus developed into embryogenic callus,which was used to establish cell suspension lines.Cell suspensions had to be subcultured at a interval of 4-5 days at the first several culture cycles.The best subculturing cycle for the stable cell suspensions was 8-10 days.The best inoculum quantity was 1 mL PCV(Packed Cell Volume) per 40 mL culture fluid.

  5. Next Generation Suspension Dynamics Algorithms

    Energy Technology Data Exchange (ETDEWEB)

    Schunk, Peter Randall [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Higdon, Jonathon [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Chen, Steven [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)

    2014-12-01

    This research project has the objective to extend the range of application, improve the efficiency and conduct simulations with the Fast Lubrication Dynamics (FLD) algorithm for concentrated particle suspensions in a Newtonian fluid solvent. The research involves a combination of mathematical development, new computational algorithms, and application to processing flows of relevance in materials processing. The mathematical developments clarify the underlying theory, facilitate verification against classic monographs in the field and provide the framework for a novel parallel implementation optimized for an OpenMP shared memory environment. The project considered application to consolidation flows of major interest in high throughput materials processing and identified hitherto unforeseen challenges in the use of FLD in these applications. Extensions to the algorithm have been developed to improve its accuracy in these applications.

  6. Microfluidic Bead Suspension Hopper

    OpenAIRE

    Price, Alexander K.; MacConnell, Andrew B.; Paegel, Brian M.

    2014-01-01

    Many high-throughput analytical platforms, from next-generation DNA sequencing to drug discovery, rely on beads as carriers of molecular diversity. Microfluidic systems are ideally suited to handle and analyze such bead libraries with high precision and at minute volume scales; however, the challenge of introducing bead suspensions into devices before they sediment usually confounds microfluidic handling and analysis. We developed a bead suspension hopper that exploits sedimentation to load b...

  7. The Mystical Suspension

    Directory of Open Access Journals (Sweden)

    Héctor Santiesteban Oliva

    2016-11-01

    Full Text Available Mistical suspension, silence, time, absolute, ontology, ineffability, aletheiaIn the mystical ecstasy there is a sensorial and intellectual suspension when contemplating the absolute, the ontological Being. Silence is not only significant: it is revealing. The greatest expression of experience inner silence . The word is insufficient when the ontological reality is revealed. Revelation or truth , the Greek concept of aletheia, takes on greater significance in that transcendental experience. It is also suspended phenomenological time and remains eternity open.

  8. Content research on antibody titer and plasma protein of plasma and red blood cell suspension supernatant fluid%血浆与红细胞悬液上清液中抗体效价及血浆蛋白的含量研究

    Institute of Scientific and Technical Information of China (English)

    赵敏

    2012-01-01

      目的分析红细胞悬浮液与血浆对应的抗体效价及其蛋白含量.方法随机收集无偿献血者261名.针对各全血制备对应的血浆和红细胞悬浮液,检测各血上清的抗A、抗B效价及其对应的血浆蛋白含量并比较分析.结果 A型血浆抗B效价的效价为31.05±20.29,A型红细胞悬液抗B的抗体效价为5.86±3.60;B型血浆抗A的效价为21.69±18.34,B型红细胞悬液抗A的抗体效价为3.08±1.99;O型血浆抗A的效价为34.02±20.76,血浆抗B的抗体效价为31.98±19.32;O型红细胞悬液的抗体抗A效价为5.96±2.86,抗B抗体效价为5.32±2.45.A型血的血浆蛋白与红细胞悬液上清液存在显著差异,且血浆抗体的效价是红细胞上清效价均数的7倍;血浆蛋白则为红细胞悬液的5-8倍.结论与血浆比较,各血型红细胞悬浮液的抗体效价明显低,含有较少蛋白,可只用主侧配血.%  Objective To analyse the antibody titer and its protein content of red blood cell suspension and plasma corresponding. Methods Random collect voluntary blood donors 261. On the whole blood preparation corresponding plasma and erythrocytes suspension, detecting the blood supernatant of A resistance, resistance to B valence and the corresponding plasma protein content and comparative analysis. Results The results showed that the type A plasma resistance to B titer of valence was 31.05±20.29, type A red blood cell suspension resistance to B antibody titer was5.86±3.60; Type B plasma resistance to A titer was 21.69±18.34, type B cell suspension resistance to A antibody titer was 3.08±1.99; Type O blood plasma resistance to A titer was 34.02±20.76, plasma resistance to B antibody titer was 31.98±19.32; Type O red blood cell suspension antibody resistance to A titer was 5.96±2.86, resistance to B antibody titer was 5.32±2.45. Type A blood plasma protein and red blood cell suspension supernatant fluid exists significant difference, and plasma antibody

  9. Rheology in the Teaching Lab: Properties of Starch Suspensions

    CERN Document Server

    Groman, Joel A; Katz, Jonathan I

    2014-01-01

    In everyday life we encounter many complex fluids, from shear-thinning paint and toothpaste to shear-thickening starch suspensions. The study of their properties offers an opportunity for students to relate sophisticated physical concepts to their everyday experience. Modern rheology uses expensive equipment impractical for the teaching laboratory. Here we describe a rudimentary rheometer suitable for student laboratories that can demonstrate and quantify discontinuous shear thickening, the most dramatic property of complex fluids, and use it to measure the properties of starch suspensions.

  10. Electrorheology of suspensions containing interfacially active constituents.

    Science.gov (United States)

    McIntyre, Carl; Yang, Hengxi; Green, Peter F

    2013-09-25

    We recently showed that a suspension of micrometer-sized polystyrene (PS) particles in a PDMS liquid, mixed with small (1 wt %) amounts of a nanocage, sulfonated polyhedral oligomeric silsesquioxane (s-POSS), exhibited significant electrorheological (ER) behavior. This behavior was associated with the formation of a thin adsorbed layer of s-POSS onto the surfaces of PS and the subsequent formation of polarization-induced aggregates, or structures, responsible for the ER effect in an applied electric, E, field. Current theory suggests that the ER effect would largely be determined by the dielectric and conductive properties of the conductive layer of core/shell particles in ER suspensions. We show here that sulfonated-PS (s-PS)/PDMS suspensions exhibit further increases in the yield stress of over 200%, with the addition of s-POSS. The yield stress of this system, moreover, scales as τy [proportionality] E(2). The dielectric relaxation studies reveal the existence of a new relaxation peak in the s-POSS/s-PS/PDMS system that is absent in the s-POSS/PS/PDMS suspension. The relative sizes of these peaks are sensitive to the concentration of s-POSS and are associated with changes in the ER behavior. The properties of this class of ER fluids are not appropriately rationalized in terms of current theories.

  11. Magnetorheological behaviour and electrospinning of poly(ethylene oxide) suspensions with magnetic nanoparticles

    OpenAIRE

    2016-01-01

    The properties of poly(ethylene oxide) aqueous suspensions with magnetic nanoparticles synthesized under microwave-assisted radiation are studied. The magnetic nanoparticles are formed by iron (III) chloride hexahydrate (FeCl3·6H2O) dissolved in ethylene glycol (C2H4(OH)2) and subsequently in aqueous ammonia solution (approx. 25 wt% aq.). The polymer suspension exhibits substantial advantages over a suspension when 'classical' carrier fluids (water and silicone oil) are used. First, the prese...

  12. Highly conductive, printable pastes from capillary suspensions

    Science.gov (United States)

    Schneider, Monica; Koos, Erin; Willenbacher, Norbert

    2016-08-01

    We have used the capillary suspension phenomenon to design conductive pastes for printed electronic applications, such as front side metallization of solar cells, without non-volatile, organic additives that often deteriorate electrical properties. Adding a small amount of a second, immiscible fluid to a suspension creates a network of liquid bridges between the particles. This capillary force-controlled microstructure allows for tuning the flow behavior in a wide range. Yield stress and low-shear viscosity can be adjusted such that long-term stability is provided by inhibiting sedimentation, and, even more importantly, narrow line widths and high aspect ratios are accessible. These ternary mixtures, called capillary suspensions, exhibit a strong degree of shear thinning that allows for conventional coating or printing equipment to be used. Finally, the secondary fluid, beneficial for stability and processing of the wet paste, completely evaporates during drying and sintering. Thus, we obtained high purity silver and nickel layers with a conductivity two times greater than could be obtained with state-of-the-art, commercial materials. This revolutionary concept can be easily applied to other systems using inorganic or even organic conductive particles and represents a fundamental paradigm change to the formulation of pastes for printed electronics.

  13. Rheology of dense suspensions of non colloidal particles

    Science.gov (United States)

    Guazzelli, Élisabeth

    2017-06-01

    Dense suspensions are materials with broad applications both in industrial processes (e.g. waste disposal, concrete, drilling muds, metalworking chip transport, and food processing) and in natural phenomena (e.g. flows of slurries, debris, and lava). Despite its long research history and its practical relevance, the mechanics of dense suspensions remain poorly understood. The major difficulty is that the grains interact both by hydrodynamic interactions through the liquid and by mechanical contact. These systems thus belong to an intermediate regime between pure suspensions and granular flows. We show that we can unify suspension and granular rheology under a common framework by transferring the frictional approach of dry granular media to wet suspensions of spherical particles. We also discuss non-Newtonian behavior such as normal-stress differences and shear-induced migration. Beyond the classical problem of dense suspension of hard spheres which is far from being completely resolved, there are also entirely novel avenues of study concerning more complex mixtures of particles and fluids such as those involving other types of particles (e.g. fibers) or non-Newtonian fluids that we will also address.

  14. Rheology of dense suspensions of non colloidal particles

    Directory of Open Access Journals (Sweden)

    Guazzelli Élisabeth

    2017-01-01

    Full Text Available Dense suspensions are materials with broad applications both in industrial processes (e.g. waste disposal, concrete, drilling muds, metalworking chip transport, and food processing and in natural phenomena (e.g. flows of slurries, debris, and lava. Despite its long research history and its practical relevance, the mechanics of dense suspensions remain poorly understood. The major difficulty is that the grains interact both by hydrodynamic interactions through the liquid and by mechanical contact. These systems thus belong to an intermediate regime between pure suspensions and granular flows. We show that we can unify suspension and granular rheology under a common framework by transferring the frictional approach of dry granular media to wet suspensions of spherical particles. We also discuss non-Newtonian behavior such as normal-stress differences and shear-induced migration. Beyond the classical problem of dense suspension of hard spheres which is far from being completely resolved, there are also entirely novel avenues of study concerning more complex mixtures of particles and fluids such as those involving other types of particles (e.g. fibers or non-Newtonian fluids that we will also address.

  15. Dynamic shear jamming in dense granular suspensions under extension

    Science.gov (United States)

    Majumdar, Sayantan; Peters, Ivo R.; Han, Endao; Jaeger, Heinrich M.

    2017-01-01

    Unlike dry granular materials, a dense granular suspension like cornstarch in water can strongly resist extensional flows. At low extension rates, such a suspension behaves like a viscous fluid, but rapid extension results in a response where stresses far exceed the predictions of lubrication hydrodynamics and capillarity. To understand this remarkable mechanical response, we experimentally measure the normal force imparted by a large bulk of the suspension on a plate moving vertically upward at a controlled velocity. We observe that, above a velocity threshold, the peak force increases by orders of magnitude. Using fast ultrasound imaging we map out the local velocity profiles inside the suspension, which reveal the formation of a growing jammed region under rapid extension. This region interacts with the rigid boundaries of the container through strong velocity gradients, suggesting a direct connection to the recently proposed shear-jamming mechanism.

  16. Rheology of organoclay suspension

    CSIR Research Space (South Africa)

    Hato, MJ

    2011-05-01

    Full Text Available -1 Colloid & Polymer Science Volume 289, Number 10, 1119-1125, DOI: 10.1007/s00396-011-2438-4 Rheology of organoclay suspension Mpitloane Joseph Hato, Ke Zhang, Suprakas Sinha Ray and Hyoung Jin Choi Abstract We have studied the rheological...

  17. Alternatives to Student Suspension

    Science.gov (United States)

    Robinett, David

    2012-01-01

    Seven years ago, James A. Garfield High School in East Los Angeles set a school record with 613 student suspensions, out of a total enrollment of 5,000 students. The school, made famous by the 1988 film "Stand and Deliver", was no stranger to the high rates of student discipline all too common within the Los Angeles Unified School…

  18. Breaker turbulence and sediment suspension in the surf zone

    DEFF Research Database (Denmark)

    Aagaard, Troels; Hughes, Michael G

    2010-01-01

    Field measurements of fluid velocities and suspended sediment concentrations were used to investigate the relative role of coherent vortices (related to wave breaking) in suspended sediment dynamics. The measurements were obtained from a barred (intermediate-type) beach and the instrument rig was...... between the horizontal fluid velocity and vortex-induced sediment suspension for each of the wave types, which may contribute to an explanation of net offshore and onshore sediment transport observed during episodes of beach erosion and recovery, respectively....

  19. Cryonic Suspension and the Law.

    Science.gov (United States)

    Smith, George P.; Hall, Clare

    1987-01-01

    Analyzes three central problems which adversely affect use, development, and perfection of cryonic suspension of individuals: the extent to which a physician may be guilty of malpractice in assisting with a suspension; the need for a recognition of suspension; and the present effect of the law's anachronistic treatment of estate devolution upon a…

  20. Main resonance analysis for a MR suspension system with slowly varying parameters%参数慢变磁流变非线性悬架系统主共振研究

    Institute of Scientific and Technical Information of China (English)

    董小闵; 王小龙; 古晓科

    2014-01-01

    The output damping force of a magneto-rheological (MR)damper is reduced with increase in working temperature.As a result,the performance of a MR suspension system is degraded.On the basis of the theory of heat transfer and nonlinear vibration,the main resonance of a MR suspension dynamic system with slowly varying parameters was analyzed here.The energy differential equations at the working area of the MR damper were established and solved with the numerical method.The modified Bingham model was applied to calculate the output damping force of the MR damper.The nonlinear dynamic equation of the MR suspension system with slowly varying parameters was formulated.The steady amplitude response of the MR suspension system under the excitation of main resonance was solved with the averaging method.The calculated results showed that the working temperature rises with increase in running time of the MR damper,consequently,the output damping force of the MR damper decreases significantly and the vibration amplitude variation of the suspension system increases,the performance of the MR suspension system is degraded.%针对磁流变阻尼器随工作温度变化导致阻尼力发生改变,进而降低磁流变悬架系统性能的问题,基于传热学方程和参数慢变非线性振动理论研究温度变化对磁流变非线性悬架系统的主共振动力学行为的影响。根据传热学理论建立磁流变阻尼器工作区域能量微分方程,用数值方法求出温度变化规律,用改进的Bingham模型计算磁流变阻尼力;建立慢变参数磁流变非线性悬架系统动力学方程,利用平均法求解主共振激励下的悬架动行程的稳态幅值响应。研究表明:随着运行时间增加,磁流变阻尼器的温度逐渐升高,导致磁流变阻尼力大幅降低,悬架动行程稳态振幅及其变化量越大,从而使得悬架系统的性能偏离设计目标。

  1. Superfluid Behavior of Active Suspensions from Diffusive Stretching

    Science.gov (United States)

    Takatori, S. C.; Brady, J. F.

    2017-01-01

    The current understanding is that the non-Newtonian rheology of active matter suspensions is governed by fluid-mediated hydrodynamic interactions associated with active self-propulsion. Here we discover an additional contribution to the suspension shear stress that predicts both thickening and thinning behavior, even when there is no nematic ordering of the microswimmers with the imposed flow. A simple micromechanical model of active Brownian particles in homogeneous shear flow reveals the existence of off-diagonal shear components in the swim stress tensor, which are independent of hydrodynamic interactions and fluid disturbances. Theoretical predictions from our model are consistent with existing experimental measurements of the shear viscosity of active suspensions, but also suggest new behavior not predicted by conventional models.

  2. Heat transfer in suspensions of rigid particles

    Science.gov (United States)

    Brandt, Luca; Niazi Ardekani, Mehdi; Abouali, Omid

    2016-11-01

    We study the heat transfer in laminar Couette flow of suspensions of rigid neutrally buoyant particles by means of numerical simulations. An Immersed Boundary Method is coupled with a VOF approach to simulate the heat transfer in the fluid and solid phase, enabling us to fully resolve the heat diffusion. First, we consider spherical particles and show that the proposed algorithm is able to reproduce the correlations between heat flux across the channel, the particle volume fraction and the heat diffusivity obtained in laboratory experiments and recently proposed in the literature, results valid in the limit of vanishing inertia. We then investigate the role of inertia on the heat transfer and show an increase of the suspension diffusivity at finite particle Reynolds numbers. Finally, we vary the relativity diffusivity of the fluid and solid phase and investigate its effect on the effective heat flux across the channel. The data are analyzed by considering the ensemble averaged energy equation and decomposing the heat flux in 4 different contributions, related to diffusion in the solid and fluid phase, and the correlations between wall-normal velocity and temperature fluctuations. Results for non-spherical particles will be examined before the meeting. Supported by the European Research Council Grant No. ERC-2013- CoG-616186, TRITOS. The authors acknowledge computer time provided by SNIC (Swedish National Infrastructure for Computing).

  3. Bubble wake dynamics in liquids and liquid-solid suspensions

    CERN Document Server

    Fan, Liang-Shih; Brenner, Howard

    1990-01-01

    This book is devoted to a fundamental understanding of the fluid dynamic nature of a bubble wake, more specifically the primary wake, in liquids and liquid-solid suspensions, an dto the role it plays in various important flow phenomena of multiphase systems. Examples of these phenomena are liquid/solids mixing, bubble coalescence and disintergration, particle entrainment to the freeboard, and bed contraction.

  4. Viscosity Reduction in Liquid Suspensions by Electric or Magnetic Fields

    Science.gov (United States)

    Tao, R.; Xu, X.

    Reducing the viscosity of liquid suspensions is of great importance in science and engineering. We present a theory and experiments that a suitable electric or magnetic field pulse can effectively reduce the viscosity for several hours with no appreciable change of temperature. Positive experimental results with magnetorheological fluids and crude oil suggest a broad range of practical applications.

  5. Conductivity maximum in a charged colloidal suspension

    Energy Technology Data Exchange (ETDEWEB)

    Bastea, S

    2009-01-27

    Molecular dynamics simulations of a charged colloidal suspension in the salt-free regime show that the system exhibits an electrical conductivity maximum as a function of colloid charge. We attribute this behavior to two main competing effects: colloid effective charge saturation due to counterion 'condensation' and diffusion slowdown due to the relaxation effect. In agreement with previous observations, we also find that the effective transported charge is larger than the one determined by the Stern layer and suggest that it corresponds to the boundary fluid layer at the surface of the colloidal particles.

  6. Numerical homogenization on approach for stokesian suspensions.

    Energy Technology Data Exchange (ETDEWEB)

    Haines, B. M.; Berlyand, L. V.; Karpeev, D. A. (Mathematics and Computer Science); (Department of Mathematics, Pennsylvania State Univ.)

    2012-01-20

    In this technical report we investigate efficient methods for numerical simulation of active suspensions. The prototypical system is a suspension of swimming bacteria in a Newtonian fluid. Rheological and other macroscopic properties of such suspensions can differ dramatically from the same properties of the suspending fluid alone or of suspensions of similar but inactive particles. Elongated bacteria, such as E. coli or B. subtilis, swim along their principal axis, propelling themselves with the help of flagella, attached at the anterior of the organism and pushing it forward in the manner of a propeller. They interact hydrodynamically with the surrounding fluid and, because of their asymmetrical shape, have the propensity to align with the local flow. This, along with the dipolar nature of bacteria (the two forces a bacterium exerts on a fluid - one due to self-propulsion and the other opposing drag - have equal magnitude and point in opposite directions), causes nearby bacteria to tend to align, resulting in a intermittent local ordering on the mesoscopic scale, which is between the microscopic scale of an individual bacterium and the macroscopic scale of the suspension (e.g., its container). The local ordering is sometimes called a collective mode or collective swimming. Thanks to self-propulsion, collective modes inject momentum into the fluid in a coherent way. This enhances the local strain rate without changing the macroscopic stress applied at the boundary of the container. The macroscopic effective viscosity of the suspension is defined roughly as the ratio of the applied stress to the bulk strain rate. If local alignment and therefore local strain-rate enhancement, are significant, the effective viscosity can be appreciably lower than that of the corresponding passive suspension or even of the surrounding fluid alone. Indeed, a sevenfold decrease in the effective viscosity was observed in experiments with B. subtilis. More generally, local collective

  7. Active colloids in complex fluids

    CERN Document Server

    Patteson, Alison E; Arratia, Paulo E

    2016-01-01

    We review recent work on active colloids or swimmers, such as self-propelled microorganisms, phoretic colloidal particles, and artificial micro-robotic systems, moving in fluid-like environments. These environments can be water-like and Newtonian but can frequently contain macromolecules, flexible polymers, soft cells, or hard particles, which impart complex, nonlinear rheological features to the fluid. While significant progress has been made on understanding how active colloids move and interact in Newtonian fluids, little is known on how active colloids behave in complex and non-Newtonian fluids. An emerging literature is starting to show how fluid rheology can dramatically change the gaits and speeds of individual swimmers. Simultaneously, a moving swimmer induces time dependent, three dimensional fluid flows, that can modify the medium (fluid) rheological properties. This two-way, non-linear coupling at microscopic scales has profound implications at meso- and macro-scales: steady state suspension proper...

  8. Hybrid Secondary Suspension Systems

    Directory of Open Access Journals (Sweden)

    Nader Vahdati

    2009-01-01

    Full Text Available Passive fluid mounts are used in the fixed wing applications as engine mounts. The passive fluid mount is placed in between the engine and the fuselage to reduce the cabin's structure- borne noise and vibration generated by the engine.

  9. Determination of the suspension competence of debris flows based on particle size analysis

    Institute of Scientific and Technical Information of China (English)

    Hong-juan YANG; Fang-qiang WEI; Kai-heng HU; Chuan-chang WANG

    2014-01-01

    The determination of the critical particle size between solid and fluid phases, i.e., the suspension competence, is fundamental for debris flow. A method for determining suspension competence based on particle size analysis is presented in this paper. Suspension competence of static experimental water-debris mixtures prepared with the sediment of Jiangjia Gully is~0.025 mm if the bulk density is less than 1,800 kg m-3 and it increases with bulk density of more concentrated mixtures. Suspension competence of natural debris flows in Jiangjia Gully increases exponentially with the bulk density. These two data sets are compared in order to understand the suspension mechanism. It is concluded that turbulence may play a leading role in particle suspension in non-viscous and sub-viscous debris flows, while in viscous debris flows both matrix strength and excess pore water pressure play important roles.

  10. An Analysis of Electrophoresis of Concentrated Suspensions of Colloidal Particles.

    Science.gov (United States)

    Johnson; Davis

    1999-07-15

    An analysis of the electrophoretic motion of charged colloidal particles in a concentrated suspension is developed to predict the electrophoretic mobility of the particles and the electrical conductivity of the suspension. The analysis is based on a unit cell model that takes into account particle-particle hydrodynamic interactions and includes relatively thick electric double layers. The fluid motion in the unit cell is treated by writing the relevant Navier-Stokes equation in terms of the stream function and vorticity. The governing equations were then solved by a finite-difference method. The calculated electrophoretic mobilities are in agreement with prior analytical solutions for moderately concentrated suspensions, and the theory reduces to the result of O'Brien and White for low to moderate zeta potentials and dilute suspensions and to the classical result of Smoluchowski for thin double layers and dilute suspensions. A parametric study shows that the electrical conductivity of the suspension relative to a free electrolyte solution is affected by the counterion to co-ion diffusivity ratio, the double-layer thickness, and the volume fraction of particles. For a dispersion of moderately charged particles (moderate zeta potentials) with thick double layers, the numerical model predicts the electrical conductivity in agreement with experimental values reported in the literature. Copyright 1999 Academic Press.

  11. Analysis of Train Suspension System Using MR dampers

    Science.gov (United States)

    RamaSastry, DVA; Ramana, K. V.; Mohan Rao, N.; Siva Kumar, SVR; Priyanka, T. G. L.

    2016-09-01

    This paper deals with introducing MR dampers to the Train Suspension System for improving the ride comfort of the passengers. This type of suspension system comes under Semi-active suspension system which utilizes the properties of MR fluid to damp the vibrations. In case of high speed trains, the coach body is subjected to vibrations due to vertical displacement, yaw and pitch movements. When the body receives these disturbances from the ground,the transmission of vibrations to the passenger increases which affect the ride comfort. In this work, the equations of motion of suspension system are developed for both conventional passive system and semi-active system and are modelled in Matlab/Simulink and analysis has been carried out. The passive suspension system analysis shows that it is taking more time to damp the vibrations and at the same time the transmissibility of vibrations is more.Introducing MR dampers,vertical and angular displacements of the body are computed and compared. The results show that the introduction of MR dampers into the train suspension system improves ride comfort.

  12. A magnetic suspension system for measuring liquid density

    Directory of Open Access Journals (Sweden)

    Luz María Centeno González

    2013-04-01

    Full Text Available Density is a derived quantity of mass and length; it is defined as mass per volume unit and its SI unit is kg/m3. National metrology institutes have been designing and building their own magnetic suspension systems during the last 5 decades for making fluid density measurements; this has allowed them to carry out research into liquids and gases’ physical characteristics. This paper was aimed at designing and developing a magnetic suspension system for a magnetic balance used in determining liquid density to be used in CENAM’s metrology density laboratories.

  13. 磁流变液技术及其工程应用研究综述

    Institute of Scientific and Technical Information of China (English)

    郑祥盘; 郭源帆; 陈淑梅

    2011-01-01

    磁流变液是一种性能独特的智能流变材料.能耗量、动力学性能及精确性为下一代产品的3大性能指标,而基于磁流变液结构的产品在未来的工程实践中将有广阔的应用前景.介绍磁流变液的组成、流变特性与工作机理.在分析磁流变液装置工作模式的基础上,对近来基于磁流变液的应用领域进行分类和全面论述,指出目前磁流变液技术在发展中存在的问题及今后的发展方向.%Magneto-rheological fluid is a unique type of intelligent rheological materials in terms of its function and performance. Its energy consumption, dynamic performance and accuracy have become 3 major function indicators for the next product generation. Nevertheless, products based on mechanical construction with magneto-rheological fluid will have a broad application prospect in engineering practice in the future. The text introduces composition, Theological properties, and working mechanisms of the magneto-rheological fluid. Based on analyzing work mode of the magneto-rheological fluid device, the text carries out classification and full description on usage areas of the magneto-rheological fluid while pointing out problems existing in the development as well the developing tendency of the magneto-rheological fluid technology in the future.

  14. CFD simulation of particle suspension in a stirred tank

    Institute of Scientific and Technical Information of China (English)

    Nana Qi; Hu Zhang; Kai Zhang; Gang Xu; Yongping Yang

    2013-01-01

    Particle suspension characteristics are predicted computationally in a stirred tank driven by a Smith turbine.In order to verify the hydrodynamic model and numerical method,the predicted power number and flow pattern are compared with designed values and simulated results from the literature,respectively.The effects of particle density,particle diameter,liquid viscosity and initial solid loading on particle suspension behavior are investigated by using the Eulerian-Eulerian two-fluid model and the standard k-ε turbulence model.The results indicate that solid concentration distribution depends on the flow field in the stirred tank.Higher particle density or larger particle size results in less homogenous distribution of solid particles in the tank.Increasing initial solid loading has an adverse impact on the homogeneous suspension of solid particles in a low-viscosity liquid,whilst more uniform particle distribution is found in a high-viscositv liauid.

  15. Simulating flexible fiber suspensions using a scalable immersed boundary algorithm

    CERN Document Server

    Wiens, Jeffrey K

    2014-01-01

    We present an approach for numerically simulating the dynamics of flexible fibers in a three-dimensional shear flow using a scalable immersed boundary (IB) algorithm based on Guermond and Minev's pseudo-compressible fluid solver. The fibers are treated as one-dimensional Kirchhoff rods that resist stretching, bending, and twisting, within the generalized IB framework. We perform a careful numerical comparison against experiments on single fibers performed by S. G. Mason and co-workers, who categorized the fiber dynamics into several distinct orbit classes. We show that the orbit class may be determined using a single dimensionless parameter for low Reynolds flows. Lastly, we simulate dilute suspensions containing up to hundreds of fibers using a distributed- memory computer cluster. These simulations serve as a stepping stone for studying more complex suspension dynamics including non-dilute suspensions and aggregation of fibers (also known as flocculation).

  16. Hydrodynamic length-scale selection in microswimmer suspensions

    Science.gov (United States)

    Heidenreich, Sebastian; Dunkel, Jörn; Klapp, Sabine H. L.; Bär, Markus

    2016-08-01

    A universal characteristic of mesoscale turbulence in active suspensions is the emergence of a typical vortex length scale, distinctly different from the scale invariance of turbulent high-Reynolds number flows. Collective length-scale selection has been observed in bacterial fluids, endothelial tissue, and active colloids, yet the physical origins of this phenomenon remain elusive. Here, we systematically derive an effective fourth-order field theory from a generic microscopic model that allows us to predict the typical vortex size in microswimmer suspensions. Building on a self-consistent closure condition, the derivation shows that the vortex length scale is determined by the competition between local alignment forces, rotational diffusion, and intermediate-range hydrodynamic interactions. Vortex structures found in simulations of the theory agree with recent measurements in Bacillus subtilis suspensions. Moreover, our approach yields an effective viscosity enhancement (reduction), as reported experimentally for puller (pusher) microorganisms.

  17. Particle-wall tribology of slippery hydrogel particle suspensions.

    Science.gov (United States)

    Shewan, Heather M; Stokes, Jason R; Cloitre, Michel

    2017-02-22

    Slip is an important phenomenon that occurs during the flow of yield stress fluids like soft materials and pastes. Densely packed suspensions of hydrogel microparticles are used to show that slip is governed by the tribological interactions occurring between the samples and shearing surfaces. Both attractive/repulsive interactions between the dispersed particles and surface, as well as the viscoelasticity of the suspension, are found to play key roles in slip occurring within rheometric flows. We specifically discover that for two completely different sets of microgels, the sliding stress at which slip occurs scales with both the modulus of the particles and the bulk suspension modulus. This suggests that hysteresis losses within the viscoelastic particles contribute to friction forces and thus slip at the particle-surface tribo-contact. It is also found that slip during large amplitude oscillatory shear and steady shear flows share the same generic features.

  18. 48 CFR 209.407 - Suspension.

    Science.gov (United States)

    2010-10-01

    ... 48 Federal Acquisition Regulations System 3 2010-10-01 2010-10-01 false Suspension. 209.407... OF DEFENSE ACQUISITION PLANNING CONTRACTOR QUALIFICATIONS Debarment, Suspension, and Ineligibility 209.407 Suspension....

  19. 75 FR 27923 - Nonprocurement Debarment and Suspension

    Science.gov (United States)

    2010-05-19

    ... 3150-AI76 Nonprocurement Debarment and Suspension AGENCY: Nuclear Regulatory Commission. ACTION: Final... nonprocurement debarment and suspension. These regulations cover grants, cooperative agreements and other...) guidance on nonprocurement debarment and suspension found in OMB's regulations. DATES: Effective June...

  20. Vehicle with tilting suspension system

    OpenAIRE

    Festini, Andrea; Tonoli, Andrea; Cavalli, Fabio; Carabelli, Stefano

    2006-01-01

    The patent is relative to the application of a tilting suspension on a snowmobile to improve its drive feeling and safety. At high speed the introduction of the tilting suspension reduce the rollover risk during cornering. The vehicle can tilt as a motorcycle and its lateral dimensions can be reduced not compromising the vehicle stability

  1. Refrigerating fluids; Fluides frigorigenes

    Energy Technology Data Exchange (ETDEWEB)

    Anon.

    1999-03-01

    Refrigerating fluids are experiencing a real revolution since few years. CFCs with their destructive effect on the ozone layer are now prohibited while HCFCs will be progressively eliminated and replaced by HFCs. However, HFCs can contribute to the increase of the greenhouse effect. The solutions proposed by thermal engineering professionals consist in the confinement of air-conditioning installations (elimination of recurrent leaks) and in the improvement of installations efficiency. HCFC fluids like the R 22 are still widely used in air-conditioning but they are supposed to be replaced by HFC fluids like the R 134a, the R 407C or the R 410A. This short paper gives a brief presentation of these fluids and of their chemical characteristics. (J.S.)

  2. Self-Suspended Suspensions of Covalently Grafted Hairy Nanoparticles

    KAUST Repository

    Choudhury, Snehashis

    2015-03-17

    © 2015 American Chemical Society. Dispersions of small particles in liquids have been studied continuously for almost two centuries for their ability to simultaneously advance understanding of physical properties of fluids and their widespread use in applications. In both settings, the suspending (liquid) and suspended (solid) phases are normally distinct and uncoupled on long length and time scales. In this study, we report on the synthesis and physical properties of a novel family of covalently grafted nanoparticles that exist as self-suspended suspensions with high particle loadings. In such suspensions, we find that the grafted polymer chains exhibit unusual multiscale structural transitions and enhanced conformational stability on subnanometer and nanometer length scales. On mesoscopic length scales, the suspensions display exceptional homogeneity and colloidal stability. We attribute this feature to steric repulsions between grafted chains and the space-filling constraint on the tethered chains in the single-component self-suspended materials, which inhibits phase segregation. On macroscopic length scales, the suspensions exist as neat fluids that exhibit soft glassy rheology and, counterintuitively, enhanced elasticity with increasing temperature. This feature is discussed in terms of increased interpenetration of the grafted chains and jamming of the nanoparticles. (Chemical Presented).

  3. The convective dynamics of a suspension of ice crystals

    Science.gov (United States)

    Rees Jones, David; Wells, Andrew

    2014-11-01

    The formation of solid crystals from a liquid cooled beneath its freezing temperature occurs in a wide range of environmental and industrial situations, such as in the formation of so-called ``frazil ice'' in rivers and the polar oceans. Eddies in the fluid flow act to keep the crystals suspended, while the relative buoyancy of the crystals causes them to rise, eventually sedimenting to form a layer of ice, called grease ice in the oceans. Here, we consider the interaction between the fluid dynamics of a suspension of crystals and the thermodynamics of phase change governing the growth and melting of the crystals. The crystals grow when the local temperature lies below the freezing temperature and melt when it lies above. We explore simplified scenarios that illustrate the important features of this multiphase flow and the effect of this ``active suspension'' on heat transfer. This research is funded by the John Fell Oxford University Press (OUP) Research Fund.

  4. Fabrication and investigation on field-dependent properties of natural rubber based magneto-rheological elastomer isolator

    Science.gov (United States)

    Ain Abd Wahab, Nurul; Amri Mazlan, Saiful; Ubaidillah; Kamaruddin, Shamsul; Intan Nik Ismail, Nik; Choi, Seung-Bok; Haziq Rostam Sharif, Amirul

    2016-10-01

    This study presents a laminated magnetorheological elastomer (MRE) isolator which applies to vibration control in practice. The proposed isolator is fabricated with multilayer MRE sheets associated with the natural rubber (NR) as a matrix, and steel plates. The fabricated MRE isolator is then magnetically analysed to achieve high magnetic field intensity which can produce high damping force required for effective vibration control. Subsequently, the NR-based MRE specimen is tested to identify the field-dependent rheological properties such as storage modulus with 60 weight percentage of carbonyl iron particles. It is shown from this test that the MR effect of MRE specimen is quantified to reach up to 120% at 0.8 T. Following the design stage, the electromagnetic simulation using the finite element method magnetic (FEMM) software is carried out for analysing the magnetic flux distribution in the laminated MRE isolator. The laminated MRE isolator is then examined to a series of compression for static and dynamic test under various applied currents using the dynamic fatigue machine and biaxial dynamic testing machine. It is shown that the static compression force is increased by 14.5% under strong magnetic field compared to its off-state. Meanwhile, the dynamic compression test results show that the force increase of the laminated MRE isolator is up to 16% and 7% for low and high frequency respectively. From the results presented in this work, it is demonstrated that the full-scale concept of the MRE isolator can be one of the potential candidates for vibration control applications by tunability of the dynamic stiffness.

  5. Rheological Characterization of Polyoxyethylene (POE) and Carboxymethyl Cellulose (CMC) Suspensions with Added Solids

    Science.gov (United States)

    Mora, A.; Skurtys, O.; Osorio, F.

    2015-04-01

    The rheological properties of high molecular weight POE and CMC suspensions by adding micro-metric solid particles such as fibers or spheres were studied. The volume fraction, Φ, was varied between 0 and 0.4. Their rheological properties were obtained after fitting a Cross model. For POE suspending fluid with spherical particle, the behavior of the normalized steady shear viscosity, μ/μ0, as function of the fraction volume followed a Thomas model. However, for CMC suspensions, μ/μ0 seems to be lineal with Φ. For a pure fluid or a suspension with Φ = 0; 2, the suspension presented an elastic behavior whereas it was observed a viscous behavior when the volume fraction was increased.

  6. Scattering series in the mobility problem for suspensions

    Science.gov (United States)

    Makuch, Karol

    2012-11-01

    The mobility problem for suspensions of spherical particles immersed in an arbitrary flow of a viscous, incompressible fluid is considered in the regime of low Reynolds numbers. The scattering series which appears in the mobility problem is simplified. The simplification relies on the reduction of the number of types of single-particle scattering operators appearing in the scattering series. In our formulation there is only one type of single-particle scattering operator.

  7. Unifying suspension and granular rheology.

    Science.gov (United States)

    Boyer, François; Guazzelli, Élisabeth; Pouliquen, Olivier

    2011-10-28

    Using an original pressure-imposed shear cell, we study the rheology of dense suspensions. We show that they exhibit a viscoplastic behavior similarly to granular media successfully described by a frictional rheology and fully characterized by the evolution of the friction coefficient μ and the volume fraction ϕ with a dimensionless viscous number I(v). Dense suspension and granular media are thus unified under a common framework. These results are shown to be compatible with classical empirical models of suspension rheology and provide a clear determination of constitutive laws close to the jamming transition.

  8. Intense sediment transport: Collisional to turbulent suspension

    Science.gov (United States)

    Berzi, Diego; Fraccarollo, Luigi

    2016-02-01

    A recent simple analytical approach to the problem of steady, uniform transport of sediment by a turbulent shearing fluid dominated by interparticle collisions is extended to the case in which the mean turbulent lift may partially or totally support the weight of the sediment. We treat the granular-fluid mixture as a continuum and make use of constitutive relations of kinetic theory of granular gases to model the particle phase and a simple mixing-length approach for the fluid. We focus on pressure-driven flows over horizontal, erodible beds and divide the flow itself into layers, each dominated by different physical mechanisms. This permits a crude analytical integration of the governing equations and to obtain analytical expressions for the distribution of particle concentration and velocity. The predictions of the theory are compared with existing laboratory measurements on the flow of glass spheres and sand particles in water. We also show how to build a regime map to distinguish between collisional, turbulent-collisional, and fully turbulent suspensions.

  9. Engineering Fracking Fluids with Computer Simulation

    Science.gov (United States)

    Shaqfeh, Eric

    2015-11-01

    There are no comprehensive simulation-based tools for engineering the flows of viscoelastic fluid-particle suspensions in fully three-dimensional geometries. On the other hand, the need for such a tool in engineering applications is immense. Suspensions of rigid particles in viscoelastic fluids play key roles in many energy applications. For example, in oil drilling the ``drilling mud'' is a very viscous, viscoelastic fluid designed to shear-thin during drilling, but thicken at stoppage so that the ``cuttings'' can remain suspended. In a related application known as hydraulic fracturing suspensions of solids called ``proppant'' are used to prop open the fracture by pumping them into the well. It is well-known that particle flow and settling in a viscoelastic fluid can be quite different from that which is observed in Newtonian fluids. First, it is now well known that the ``fluid particle split'' at bifurcation cracks is controlled by fluid rheology in a manner that is not understood. Second, in Newtonian fluids, the presence of an imposed shear flow in the direction perpendicular to gravity (which we term a cross or orthogonal shear flow) has no effect on the settling of a spherical particle in Stokes flow (i.e. at vanishingly small Reynolds number). By contrast, in a non-Newtonian liquid, the complex rheological properties induce a nonlinear coupling between the sedimentation and shear flow. Recent experimental data have shown both the shear thinning and the elasticity of the suspending polymeric solutions significantly affects the fluid-particle split at bifurcations, as well as the settling rate of the solids. In the present work, we use the Immersed Boundary Method to develop computer simulations of viscoelastic flow in suspensions of spheres to study these problems. These simulations allow us to understand the detailed physical mechanisms for the remarkable physical behavior seen in practice, and actually suggest design rules for creating new fluid recipes.

  10. Viscosity of carbon nanotube suspension using artificial neural networks with principal component analysis

    Science.gov (United States)

    Yousefi, Fakhri; Karimi, Hajir; Mohammadiyan, Somayeh

    2016-11-01

    This paper applies the model including back-propagation network (BPN) and principal component analysis (PCA) to estimate the effective viscosity of carbon nanotubes suspension. The effective viscosities of multiwall carbon nanotubes suspension are examined as a function of the temperature, nanoparticle volume fraction, effective length of nanoparticle and the viscosity of base fluids using artificial neural network. The obtained results by BPN-PCA model have good agreement with the experimental data.

  11. A conservation law model for bidensity suspensions on an incline

    Science.gov (United States)

    Wong, Jeffrey T.; Bertozzi, Andrea L.

    2016-09-01

    We study bidensity suspensions of a viscous fluid on an incline. The particles migrate within the fluid due to a combination of gravity-induced settling and shear induced migration. We propose an extension of a recent model (Murisic et al., 2013) for monodisperse suspensions to two species of particles, resulting in a hyperbolic system of three conservation laws for the height and particle concentrations. We analyze the Riemann problem and show that the system exhibits three-shock solutions representing distinct fronts of particles and liquid traveling at different speeds as well as singular shock solutions for sufficiently large concentrations, for which the mechanism is essentially the same as the single-species case. We also consider initial conditions describing a fixed volume of fluid, where solutions are rarefaction-shock pairs, and present a comparison to recent experimental results. The long-time behavior of solutions is identified for settled mono- and bidisperse suspensions and some leading-order asymptotics are derived in the single-species case for moderate concentrations.

  12. Taylor-Couette flow instabilities in neutrally-buoyant suspensions

    Science.gov (United States)

    Majji, Madhu; Banerjee, Sanjoy; Morris, Jeffrey F.

    2016-11-01

    Experimentally-determined instabilities and flow states of a neutrally-buoyant suspension are described. The flow is studied in a concentric-cylinder device with inner-to-outer cylinder ratio of 0.877 with inner cylinder rotating and outer stationary. The cylinder length to annular gap ratio is 20, while the gap to particle size ratio is approximately 30, for spherical particles of 250 μm diameter. Using a slowly increasing or decreasing Re ramp, the flow agrees with all expectations for the pure fluid, while a slowly decreasing (quasi-static) ramp is used for the suspension flow, which is found to be unstable at lower Reynolds number Re (based on the effective viscosity) than pure fluid, and exhibits spiraling and ribbon states not found for a pure fluid with only inner cylinder rotating. Strikingly, the suspension at solid fraction ϕ >= 0 . 05 goes unstable first to a nonaxisymetric state rather than axisymmetric Taylor vortices. At 0 . 1 states during quais-static ramping of Re , while for ϕ = 0 . 3 , the base state Couette flow gives way to wavy spirals (WS) at Re 80 and exhibits only the WS state up to Re = 150 . Transient behavior on sudden change of Re and particle tracking will also be presented.

  13. Startup of electrophoresis in a suspension of colloidal spheres.

    Science.gov (United States)

    Chiang, Chia C; Keh, Huan J

    2015-12-01

    The transient electrophoretic response of a homogeneous suspension of spherical particles to the step application of an electric field is analyzed. The electric double layer encompassing each particle is assumed to be thin but finite, and the effect of dynamic electroosmosis within it is incorporated. The momentum equation for the fluid outside the double layers is solved through the use of a unit cell model. Closed-form formulas for the time-evolving electrophoretic and settling velocities of the particles in the Laplace transform are obtained in terms of the electrokinetic radius, relative mass density, and volume fraction of the particles. The time scale for the development of electrophoresis and sedimentation is significantly smaller for a suspension with a higher particle volume fraction or a smaller particle-to-fluid density ratio, and the electrophoretic mobility at any instant increases with an increase in the electrokinetic particle radius. The transient electrophoretic mobility is a decreasing function of the particle volume fraction if the particle-to-fluid density ratio is relatively small, but it may increase with an increase in the particle volume fraction if this density ratio is relatively large. The particle interaction effect in a suspension on the transient electrophoresis is much weaker than that on the transient sedimentation of the particles.

  14. Thermal transport phenomena in nanoparticle suspensions

    Science.gov (United States)

    Cardellini, Annalisa; Fasano, Matteo; Bozorg Bigdeli, Masoud; Chiavazzo, Eliodoro; Asinari, Pietro

    2016-12-01

    Nanoparticle suspensions in liquids have received great attention, as they may offer an approach to enhance thermophysical properties of base fluids. A good variety of applications in engineering and biomedicine has been investigated with the aim of exploiting the above potential. However, the multiscale nature of nanosuspensions raises several issues in defining a comprehensive modelling framework, incorporating relevant molecular details and much larger scale phenomena, such as particle aggregation and their dynamics. The objectives of the present topical review is to report and discuss the main heat and mass transport phenomena ruling macroscopic behaviour of nanosuspensions, arising from molecular details. Relevant experimental results are included and properly put in the context of recent observations and theoretical studies, which solved long-standing debates about thermophysical properties enhancement. Major transport phenomena are discussed and in-depth analysis is carried out for highlighting the role of geometrical (nanoparticle shape, size, aggregation, concentration), chemical (pH, surfactants, functionalization) and physical parameters (temperature, density). We finally overview several computational techniques available at different scales with the aim of drawing the attention on the need for truly multiscale predictive models. This may help the development of next-generation nanoparticle suspensions and their rational use in thermal applications.

  15. 5 CFR 919.1015 - Suspension.

    Science.gov (United States)

    2010-01-01

    ... 5 Administrative Personnel 2 2010-01-01 2010-01-01 false Suspension. 919.1015 Section 919.1015 Administrative Personnel OFFICE OF PERSONNEL MANAGEMENT (CONTINUED) CIVIL SERVICE REGULATIONS (CONTINUED) GOVERNMENTWIDE DEBARMENT AND SUSPENSION (NONPROCUREMENT) Definitions § 919.1015 Suspension. Suspension is an...

  16. 49 CFR 238.427 - Suspension system.

    Science.gov (United States)

    2010-10-01

    ... 49 Transportation 4 2010-10-01 2010-10-01 false Suspension system. 238.427 Section 238.427... Equipment § 238.427 Suspension system. (a) General requirements. (1) Suspension systems shall be designed to... equipment. (2) Passenger equipment shall meet the safety performance standards for suspension...

  17. 78 FR 2622 - Suspension of Community Eligibility

    Science.gov (United States)

    2013-01-14

    ... SECURITY Federal Emergency Management Agency 44 CFR Part 64 Suspension of Community Eligibility AGENCY...) that are scheduled for suspension on the effective dates listed within this rule because of... measures prior to the effective suspension date given in this rule, the suspension will not occur and...

  18. 77 FR 2646 - Suspension of Community Eligibility

    Science.gov (United States)

    2012-01-19

    ... SECURITY Federal Emergency Management Agency 44 CFR Part 64 Suspension of Community Eligibility AGENCY...) that are scheduled for suspension on the effective dates listed within this rule because of... measures prior to the effective suspension date given in this rule, the suspension will not occur and...

  19. 29 CFR 1472.670 - Suspension.

    Science.gov (United States)

    2010-07-01

    ... 29 Labor 4 2010-07-01 2010-07-01 false Suspension. 1472.670 Section 1472.670 Labor Regulations... DRUG-FREE WORKPLACE (FINANCIAL ASSISTANCE) Definitions § 1472.670 Suspension. Suspension means an... CFR part 9, subpart 9.4) and the common rule, Government-wide Debarment and Suspension...

  20. 22 CFR 1008.670 - Suspension.

    Science.gov (United States)

    2010-04-01

    ... 22 Foreign Relations 2 2010-04-01 2010-04-01 true Suspension. 1008.670 Section 1008.670 Foreign... ASSISTANCE) Definitions § 1008.670 Suspension. Suspension means an action taken by a Federal agency that...-wide Debarment and Suspension (Nonprocurement), that implements Executive Order 12549 and...

  1. 75 FR 5890 - Suspension of Community Eligibility

    Science.gov (United States)

    2010-02-05

    ... SECURITY Federal Emergency Management Agency 44 CFR Part 64 Suspension of Community Eligibility AGENCY...), that are scheduled for suspension on the effective dates listed within this rule because of... measures prior to the effective suspension date given in this rule, the suspension will not occur and...

  2. 7 CFR 3017.1015 - Suspension.

    Science.gov (United States)

    2010-01-01

    ... 7 Agriculture 15 2010-01-01 2010-01-01 false Suspension. 3017.1015 Section 3017.1015 Agriculture... AGRICULTURE GOVERNMENTWIDE DEBARMENT AND SUSPENSION (NONPROCUREMENT) Definitions § 3017.1015 Suspension. Suspension is an action taken by a suspending official under subpart G of this part that...

  3. 19 CFR 146.82 - Suspension.

    Science.gov (United States)

    2010-04-01

    ... 19 Customs Duties 2 2010-04-01 2010-04-01 false Suspension. 146.82 Section 146.82 Customs Duties U... (CONTINUED) FOREIGN TRADE ZONES Penalties; Suspension; Revocation § 146.82 Suspension. (a) For cause. The... for a period not to exceed 90 days. Upon order of the Board the suspension may be continued....

  4. 50 CFR 13.27 - Permit suspension.

    Science.gov (United States)

    2010-10-01

    ... 50 Wildlife and Fisheries 1 2010-10-01 2010-10-01 false Permit suspension. 13.27 Section 13.27... GENERAL PERMIT PROCEDURES Permit Administration § 13.27 Permit suspension. (a) Criteria for suspension... Government. Such suspension shall remain in effect until the issuing officer determines that the...

  5. 15 CFR 29.670 - Suspension.

    Science.gov (United States)

    2010-01-01

    ... 15 Commerce and Foreign Trade 1 2010-01-01 2010-01-01 false Suspension. 29.670 Section 29.670... WORKPLACE (FINANCIAL ASSISTANCE) Definitions § 29.670 Suspension. Suspension means an action taken by a..., subpart 9.4) and the common rule, Government-wide Debarment and Suspension (Nonprocurement),...

  6. 39 CFR 957.27 - Suspension.

    Science.gov (United States)

    2010-07-01

    ... 39 Postal Service 1 2010-07-01 2010-07-01 false Suspension. 957.27 Section 957.27 Postal Service... SUSPENSION FROM CONTRACTING § 957.27 Suspension. (a) Any firm or individual suspended under chapter 3, section 7 of the Postal Service Purchasing Manual who believes that the suspension has not been...

  7. 48 CFR 2909.407 - Suspension.

    Science.gov (United States)

    2010-10-01

    ... 48 Federal Acquisition Regulations System 7 2010-10-01 2010-10-01 false Suspension. 2909.407... CONTRACTOR QUALIFICATIONS Debarment, Suspension, and Ineligibility 2909.407 Suspension. (a) The Senior... authorized to make an exception, regarding suspension by another agency suspending official under...

  8. 77 FR 9856 - Suspension of Community Eligibility

    Science.gov (United States)

    2012-02-21

    ... SECURITY Federal Emergency Management Agency 44 CFR Part 64 Suspension of Community Eligibility AGENCY...) that are scheduled for suspension on the effective dates listed within this rule because of... measures prior to the effective suspension date given in this rule, the suspension will not occur and...

  9. 41 CFR 105-68.1015 - Suspension.

    Science.gov (United States)

    2010-07-01

    ... 41 Public Contracts and Property Management 3 2010-07-01 2010-07-01 false Suspension. 105-68.1015 Section 105-68.1015 Public Contracts and Property Management Federal Property Management Regulations...-GOVERNMENTWIDE DEBARMENT AND SUSPENSION (NONPROCUREMENT) Definitions § 105-68.1015 Suspension. Suspension is...

  10. 29 CFR 98.1015 - Suspension.

    Science.gov (United States)

    2010-07-01

    ... 29 Labor 1 2010-07-01 2010-07-01 true Suspension. 98.1015 Section 98.1015 Labor Office of the Secretary of Labor GOVERNMENTWIDE DEBARMENT AND SUSPENSION (NONPROCUREMENT) Definitions § 98.1015 Suspension. Suspension is an action taken by a suspending official under subpart G of this part that...

  11. 2 CFR 182.670 - Suspension.

    Science.gov (United States)

    2010-01-01

    ... 2 Grants and Agreements 1 2010-01-01 2010-01-01 false Suspension. 182.670 Section 182.670 Grants... Suspension. Suspension means an action taken by a Federal agency that immediately prohibits a recipient from... guidance on nonprocurement debarment and suspension (2 CFR part 180, which implements Executive...

  12. 28 CFR 83.670 - Suspension.

    Science.gov (United States)

    2010-07-01

    ... 28 Judicial Administration 2 2010-07-01 2010-07-01 false Suspension. 83.670 Section 83.670... WORKPLACE (GRANTS) Definitions § 83.670 Suspension. Suspension means an action taken by a Federal agency..., subpart 9.4) and the common rule, Government-wide Debarment and Suspension (Nonprocurement),...

  13. 77 FR 7537 - Suspension of Community Eligibility

    Science.gov (United States)

    2012-02-13

    ... SECURITY Federal Emergency Management Agency 44 CFR Part 64 Suspension of Community Eligibility AGENCY...) that are scheduled for suspension on the effective dates listed within this rule because of... measures prior to the effective suspension date given in this rule, the suspension will not occur and...

  14. 78 FR 2624 - Suspension of Community Eligibility

    Science.gov (United States)

    2013-01-14

    ... SECURITY Federal Emergency Management Agency 44 CFR Part 64 Suspension of Community Eligibility AGENCY...) that are scheduled for suspension on the effective dates listed within this rule because of... measures prior to the effective suspension date given in this rule, the suspension will not occur and...

  15. 31 CFR 19.1015 - Suspension.

    Science.gov (United States)

    2010-07-01

    ... 31 Money and Finance: Treasury 1 2010-07-01 2010-07-01 false Suspension. 19.1015 Section 19.1015 Money and Finance: Treasury Office of the Secretary of the Treasury GOVERNMENTWIDE DEBARMENT AND SUSPENSION (NONPROCUREMENT) Definitions § 19.1015 Suspension. Suspension is an action taken by a...

  16. 75 FR 4000 - Suspension of Community Eligibility

    Science.gov (United States)

    2010-01-26

    ... SECURITY Federal Emergency Management Agency 44 CFR Part 64 Suspension of Community Eligibility AGENCY...), that are scheduled for suspension on the effective dates listed within this rule because of... measures prior to the effective suspension date given in this rule, the suspension will not occur and ]...

  17. 22 CFR 1508.1015 - Suspension.

    Science.gov (United States)

    2010-04-01

    ... 22 Foreign Relations 2 2010-04-01 2010-04-01 true Suspension. 1508.1015 Section 1508.1015 Foreign Relations AFRICAN DEVELOPMENT FOUNDATION GOVERNMENTWIDE DEBARMENT AND SUSPENSION (NONPROCUREMENT) Definitions § 1508.1015 Suspension. Suspension is an action taken by a suspending official under subpart G...

  18. 45 CFR 1641.11 - Suspension.

    Science.gov (United States)

    2010-10-01

    ... 45 Public Welfare 4 2010-10-01 2010-10-01 false Suspension. 1641.11 Section 1641.11 Public Welfare Regulations Relating to Public Welfare (Continued) LEGAL SERVICES CORPORATION DEBARMENT, SUSPENSION AND REMOVAL OF RECIPIENT AUDITORS Suspension § 1641.11 Suspension. (a) IPAs suspended from providing...

  19. 45 CFR 1173.670 - Suspension.

    Science.gov (United States)

    2010-10-01

    ... 45 Public Welfare 3 2010-10-01 2010-10-01 false Suspension. 1173.670 Section 1173.670 Public... (FINANCIAL ASSISTANCE) Definitions § 1173.670 Suspension. Suspension means an action taken by a Federal..., subpart 9.4) and the common rule, Government-wide Debarment and Suspension (Nonprocurement),...

  20. 22 CFR 1509.670 - Suspension.

    Science.gov (United States)

    2010-04-01

    ... 22 Foreign Relations 2 2010-04-01 2010-04-01 true Suspension. 1509.670 Section 1509.670 Foreign... ASSISTANCE) Definitions § 1509.670 Suspension. Suspension means an action taken by a Federal agency that...-wide Debarment and Suspension (Nonprocurement), that implements Executive Order 12549 and...

  1. 43 CFR 43.670 - Suspension.

    Science.gov (United States)

    2010-10-01

    ... 43 Public Lands: Interior 1 2010-10-01 2010-10-01 false Suspension. 43.670 Section 43.670 Public... WORKPLACE (FINANCIAL ASSISTANCE) Definitions § 43.670 Suspension. Suspension means an action taken by a..., subpart 9.4) and 2 CFR part 180. Suspension of a recipient is a distinct and separate action...

  2. 49 CFR 570.61 - Suspension system.

    Science.gov (United States)

    2010-10-01

    ... 49 Transportation 6 2010-10-01 2010-10-01 false Suspension system. 570.61 Section 570.61... 10,000 Pounds § 570.61 Suspension system. (a) Suspension condition. Ball joint seals shall not be cut... bushings shall not be cracked, extruded out from or missing from suspension joints. Radius rods shall...

  3. 13 CFR 147.670 - Suspension.

    Science.gov (United States)

    2010-01-01

    ... 13 Business Credit and Assistance 1 2010-01-01 2010-01-01 false Suspension. 147.670 Section 147...-FREE WORKPLACE (NONPROCUREMENT) Definitions § 147.670 Suspension. Suspension means an action taken by a..., subpart 9.4) and the common rule, Government-wide Debarment and Suspension (Nonprocurement),...

  4. 78 FR 5734 - Suspension of Community Eligibility

    Science.gov (United States)

    2013-01-28

    ... SECURITY Federal Emergency Management Agency 44 CFR Part 64 Suspension of Community Eligibility AGENCY...) that are scheduled for suspension on the effective dates listed within this rule because of... measures prior to the effective suspension date given in this rule, the suspension will not occur and...

  5. 29 CFR 1471.1015 - Suspension.

    Science.gov (United States)

    2010-07-01

    ... 29 Labor 4 2010-07-01 2010-07-01 false Suspension. 1471.1015 Section 1471.1015 Labor Regulations Relating to Labor (Continued) FEDERAL MEDIATION AND CONCILIATION SERVICE GOVERNMENTWIDE DEBARMENT AND SUSPENSION (NONPROCUREMENT) Definitions § 1471.1015 Suspension. Suspension is an action taken by a...

  6. 2 CFR 180.1015 - Suspension.

    Science.gov (United States)

    2010-01-01

    ... 2 Grants and Agreements 1 2010-01-01 2010-01-01 false Suspension. 180.1015 Section 180.1015 Grants... Reserved OMB GUIDELINES TO AGENCIES ON GOVERNMENTWIDE DEBARMENT AND SUSPENSION (NONPROCUREMENT) Definitions § 180.1015 Suspension. Suspension is an action taken by a suspending official under subpart G of...

  7. 14 CFR 1267.670 - Suspension.

    Science.gov (United States)

    2010-01-01

    ... 14 Aeronautics and Space 5 2010-01-01 2010-01-01 false Suspension. 1267.670 Section 1267.670... WORKPLACE (FINANCIAL ASSISTANCE) Definitions § 1267.670 Suspension. Suspension means an action taken by a..., subpart 9.4) and the common rule, Government-wide Debarment and Suspension (Nonprocurement),...

  8. 31 CFR 20.670 - Suspension.

    Science.gov (United States)

    2010-07-01

    ... 31 Money and Finance: Treasury 1 2010-07-01 2010-07-01 false Suspension. 20.670 Section 20.670...-FREE WORKPLACE (FINANCIAL ASSISTANCE) Definitions § 20.670 Suspension. Suspension means an action taken..., subpart 9.4) and the common rule, Government-wide Debarment and Suspension (Nonprocurement),...

  9. 76 FR 2596 - Suspension of Community Eligibility

    Science.gov (United States)

    2011-01-14

    ... SECURITY Federal Emergency Management Agency 44 CFR Part 64 Suspension of Community Eligibility AGENCY...), that are scheduled for suspension on the effective dates listed within this rule because of... measures prior to the effective suspension date given in this rule, the suspension will not occur and...

  10. 22 CFR 208.1015 - Suspension.

    Science.gov (United States)

    2010-04-01

    ... 22 Foreign Relations 1 2010-04-01 2010-04-01 false Suspension. 208.1015 Section 208.1015 Foreign Relations AGENCY FOR INTERNATIONAL DEVELOPMENT GOVERNMENTWIDE DEBARMENT AND SUSPENSION (NONPROCUREMENT) Definitions § 208.1015 Suspension. Suspension is an action taken by a suspending official under subpart G...

  11. 29 CFR 94.670 - Suspension.

    Science.gov (United States)

    2010-07-01

    ... 29 Labor 1 2010-07-01 2010-07-01 true Suspension. 94.670 Section 94.670 Labor Office of the... § 94.670 Suspension. Suspension means an action taken by a Federal agency that immediately prohibits a... Debarment and Suspension (Nonprocurement), that implements Executive Order 12549 and Executive Order...

  12. 49 CFR 32.670 - Suspension.

    Science.gov (United States)

    2010-10-01

    ... 49 Transportation 1 2010-10-01 2010-10-01 false Suspension. 32.670 Section 32.670 Transportation... ASSISTANCE) Definitions § 32.670 Suspension. Suspension means an action taken by a Federal agency that...-wide Debarment and Suspension (Nonprocurement), that implements Executive Order 12549 and...

  13. 77 FR 2650 - Suspension of Community Eligibility

    Science.gov (United States)

    2012-01-19

    ... SECURITY Federal Emergency Management Agency 44 CFR Part 64 Suspension of Community Eligibility AGENCY...) that are scheduled for suspension on the effective dates listed within this rule because of... measures prior to the effective suspension date given in this rule, the suspension will not occur and...

  14. 21 CFR 1405.670 - Suspension.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 9 2010-04-01 2010-04-01 false Suspension. 1405.670 Section 1405.670 Food and... (FINANCIAL ASSISTANCE) Definitions § 1405.670 Suspension. Suspension means an action taken by a Federal..., subpart 9.4) and the common rule, Government-wide Debarment and Suspension (Nonprocurement),...

  15. 45 CFR 630.670 - Suspension.

    Science.gov (United States)

    2010-10-01

    ... 45 Public Welfare 3 2010-10-01 2010-10-01 false Suspension. 630.670 Section 630.670 Public Welfare... DRUG-FREE WORKPLACE (FINANCIAL ASSISTANCE) Definitions § 630.670 Suspension. Suspension means an action... CFR part 9, subpart 9.4) and the common rule, Government-wide Debarment and Suspension...

  16. 24 CFR 21.670 - Suspension.

    Science.gov (United States)

    2010-04-01

    ... 24 Housing and Urban Development 1 2010-04-01 2010-04-01 false Suspension. 21.670 Section 21.670... GOVERNMENTWIDE REQUIREMENTS FOR DRUG-FREE WORKPLACE (GRANTS) Definitions § 21.670 Suspension. Suspension means an... CFR part 9, subpart 9.4) and the common rule, Government-wide Debarment and Suspension...

  17. 7 CFR 3021.670 - Suspension.

    Science.gov (United States)

    2010-01-01

    ... 7 Agriculture 15 2010-01-01 2010-01-01 false Suspension. 3021.670 Section 3021.670 Agriculture... Suspension. Suspension means an action taken by a Federal agency that immediately prohibits a recipient from... Debarment and Suspension (Nonprocurement), that implements Executive Order 12549 and Executive Order...

  18. 22 CFR 210.670 - Suspension.

    Science.gov (United States)

    2010-04-01

    ... 22 Foreign Relations 1 2010-04-01 2010-04-01 false Suspension. 210.670 Section 210.670 Foreign... (FINANCIAL ASSISTANCE) Definitions § 210.670 Suspension. Suspension means an action taken by a Federal agency..., subpart 9.4) and the common rule, Government-wide Debarment and Suspension (Nonprocurement),...

  19. 10 CFR 607.670 - Suspension.

    Science.gov (United States)

    2010-01-01

    ... 10 Energy 4 2010-01-01 2010-01-01 false Suspension. 607.670 Section 607.670 Energy DEPARTMENT OF... ASSISTANCE) Definitions § 607.670 Suspension. Suspension means an action taken by a Federal agency that...-wide Debarment and Suspension (Nonprocurement), that implements Executive Order 12549 and...

  20. 75 FR 9111 - Suspension of Community Eligibility

    Science.gov (United States)

    2010-03-01

    ... SECURITY Federal Emergency Management Agency 44 CFR Part 64 Suspension of Community Eligibility AGENCY...), that are scheduled for suspension on the effective dates listed within this rule because of... measures prior to the effective suspension date given in this rule, the suspension will not occur and...

  1. 20 CFR 439.670 - Suspension.

    Science.gov (United States)

    2010-04-01

    ... 20 Employees' Benefits 2 2010-04-01 2010-04-01 false Suspension. 439.670 Section 439.670 Employees... ASSISTANCE) Definitions § 439.670 Suspension. Suspension means an action taken by a Federal agency that...-wide Debarment and Suspension (Nonprocurement), that implements Executive Order 12549 and...

  2. 21 CFR 1404.1015 - Suspension.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 9 2010-04-01 2010-04-01 false Suspension. 1404.1015 Section 1404.1015 Food and Drugs OFFICE OF NATIONAL DRUG CONTROL POLICY GOVERNMENTWIDE DEBARMENT AND SUSPENSION (NONPROCUREMENT) Definitions § 1404.1015 Suspension. Suspension is an action taken by a suspending official under subpart G...

  3. 34 CFR 84.670 - Suspension.

    Science.gov (United States)

    2010-07-01

    ... 34 Education 1 2010-07-01 2010-07-01 false Suspension. 84.670 Section 84.670 Education Office of... ASSISTANCE) Definitions § 84.670 Suspension. Suspension means an action taken by a Federal agency that...-wide Debarment and Suspension (Nonprocurement), that implements Executive Order 12549 and...

  4. 76 FR 9666 - Suspension of Community Eligibility

    Science.gov (United States)

    2011-02-22

    ... SECURITY Federal Emergency Management Agency 44 CFR Part 64 Suspension of Community Eligibility AGENCY...), that are scheduled for suspension on the effective dates listed within this rule because of... measures prior to the effective suspension date given in this rule, the suspension will not occur and...

  5. 22 CFR 1006.1015 - Suspension.

    Science.gov (United States)

    2010-04-01

    ... 22 Foreign Relations 2 2010-04-01 2010-04-01 true Suspension. 1006.1015 Section 1006.1015 Foreign Relations INTER-AMERICAN FOUNDATION GOVERNMENTWIDE DEBARMENT AND SUSPENSION (NONPROCUREMENT) Definitions § 1006.1015 Suspension. Suspension is an action taken by a suspending official under subpart G of...

  6. 22 CFR 312.670 - Suspension.

    Science.gov (United States)

    2010-04-01

    ... 22 Foreign Relations 2 2010-04-01 2010-04-01 true Suspension. 312.670 Section 312.670 Foreign... § 312.670 Suspension. Suspension means an action taken by a Federal agency that immediately prohibits a... Debarment and Suspension (Nonprocurement), that implements Executive Order 12549 and Executive Order...

  7. 45 CFR 1155.670 - Suspension.

    Science.gov (United States)

    2010-10-01

    ... 45 Public Welfare 3 2010-10-01 2010-10-01 false Suspension. 1155.670 Section 1155.670 Public... ASSISTANCE) Definitions § 1155.670 Suspension. Suspension means an action taken by a Federal agency that...-wide Debarment and Suspension (Nonprocurement), that implements Executive Order 12549 and...

  8. 45 CFR 1206.1-4 - Suspension.

    Science.gov (United States)

    2010-10-01

    ... 45 Public Welfare 4 2010-10-01 2010-10-01 false Suspension. 1206.1-4 Section 1206.1-4 Public... GRANTS AND CONTRACTS-SUSPENSION AND TERMINATION AND DENIAL OF APPLICATION FOR REFUNDING Suspension and Termination of Assistance § 1206.1-4 Suspension. (a) General. The responsible Corporation official may...

  9. 22 CFR 133.670 - Suspension.

    Science.gov (United States)

    2010-04-01

    ... 22 Foreign Relations 1 2010-04-01 2010-04-01 false Suspension. 133.670 Section 133.670 Foreign... ASSISTANCE) Definitions § 133.670 Suspension. Suspension means an action taken by a Federal agency that...-wide Debarment and Suspension (Nonprocurement), that implements Executive Order 12549 and...

  10. 75 FR 60 - Suspension of Community Eligibility

    Science.gov (United States)

    2010-01-04

    ... Part 64 [Docket ID FEMA-2008-0020; Internal Agency Docket No. FEMA-8111] Suspension of Community... Insurance Program (NFIP), that are scheduled for suspension on the effective dates listed within this rule... floodplain management measures prior to the effective suspension date given in this rule, the suspension...

  11. SOLID GAS SUSPENSION NUCLEAR FUEL ASSEMBLY

    Science.gov (United States)

    Schluderberg, D.C.; Ryon, J.W.

    1962-05-01

    A fuel assembly is designed for use in a gas-suspension cooled nuclear fuel reactor. The coolant fluid is an inert gas such as nitrogen or helium with particles such as carbon suspended therein. The fuel assembly is contained within an elongated pressure vessel extending down into the reactor. The fuel portion is at the lower end of the vessel and is constructed of cylindrical segments through which the coolant passes. Turbulence promotors within the passageways maintain the particles in agitation to increase its ability to transfer heat away from the outer walls. Shielding sections and alternating passageways above the fueled portion limit the escape of radiation out of the top of the vessel. (AEC)

  12. Hydrodynamic shocks in microroller suspensions

    Science.gov (United States)

    Delmotte, Blaise; Driscoll, Michelle; Chaikin, Paul; Donev, Aleksandar

    2017-09-01

    We combine experiments, large-scale simulations, and continuum models to study the emergence of coherent structures in a suspension of magnetically driven microrollers sedimented near a floor. Collective hydrodynamic effects are predominant in this system, leading to strong density-velocity coupling. We characterize a uniform suspension and show that density waves propagate freely in all directions in a dispersive fashion. When sharp density gradients are introduced in the suspension, we observe the formation of a shock. Unlike Burgers' shocklike structures observed in other active and driven confined hydrodynamic systems, the shock front in our system has a well-defined finite width and moves rapidly compared to the mean suspension velocity. We introduce a continuum model demonstrating that the finite width of the front is due to far-field nonlocal hydrodynamic interactions and governed by a geometric parameter, the average particle height above the floor.

  13. "Point de suspension"

    CERN Multimedia

    2004-01-01

    CERN - Globe of Science and Innovation 20 and 21 October Acrobatics, mime, a cappella singing, projections of images, a magical setting... a host of different tools of a grandeur matching that of the Universe they relate. A camera makes a massive zoom out to reveal the multiple dimensions of Nature. Freeze the frame: half way between the infinitesimally small and the infinitesimally large, a man suspends his everyday life (hence the title "Point de Suspension", which refers to the three dots at the end of an uncompleted sentence) to take a glimpse of the place he occupies in the great history of the Universe. An unusual perspective on what it means to be a human being... This spectacle in the Globe of Science and Innovation, specially created by the Miméscope* company for the official ceremony marking CERN's fiftieth anniversary, is a gift from the Government of the Republic and Canton of Geneva, which also wishes to share this moment of wonder with the local population. There will be three performances for...

  14. "Point de suspension"

    CERN Multimedia

    2004-01-01

    CERN - Globe of Science and Innovation 20 and 21 October Acrobatics, mime, a cappella singing, projections of images, a magical setting... a host of different tools of a grandeur matching that of the Universe they relate. A camera makes a massive zoom out to reveal the multiple dimensions of Nature. Freeze the frame: half way between the infinitesimally small and the infinitesimally large, a man suspends his everyday life (hence the title "Point de Suspension", which refers to the three dots at the end of an uncompleted sentence) to take a glimpse of the place he occupies in the great history of the Universe. An unusual perspective on what it means to be a human being... This wondrous show in the Globe of Science and Innovation, specially created by the Miméscope* company for the official ceremony marking CERN's fiftieth anniversary, is a gift from the Government of the Republic and Canton of Geneva, which also wishes to share this moment of wonder with the local population. There will be three perfo...

  15. "Point de suspension"

    CERN Multimedia

    2004-01-01

    http://www.cern.ch/cern50/ CERN - Globe of Science and Innovation 20 and 21 October Acrobatics, mime, a cappella singing, projections of images, a magical setting... a host of different tools of a grandeur matching that of the Universe they relate. A camera makes a massive zoom out to reveal the multiple dimensions of Nature. Freeze the frame: half way between the infinitesimally small and the infinitesimally large, a man suspends his everyday life (hence the title "Point de Suspension", which refers to the three dots at the end of an uncompleted sentence) to take a glimpse of the place he occupies in the great history of the Universe. An unusual perspective on what it means to be a human being... This wondrous show in the Globe of Science and Innovation, specially created by the Miméscope* company for the official ceremony marking CERN's fiftieth anniversary, is a gift from the Government of the Republic and Canton of Geneva, which also wishes to share this moment of wonder with the local pop...

  16. Amniotic fluid

    Science.gov (United States)

    ... carefully. Removing a sample of the fluid through amniocentesis can provide information about the sex, health, and development of the fetus. Images Amniocentesis Amniotic fluid Polyhydramnios Amniotic fluid References Cunningham FG, ...

  17. COUPLED CHEMOTAXIS FLUID MODEL

    KAUST Repository

    LORZ, ALEXANDER

    2010-06-01

    We consider a model system for the collective behavior of oxygen-driven swimming bacteria in an aquatic fluid. In certain parameter regimes, such suspensions of bacteria feature large-scale convection patterns as a result of the hydrodynamic interaction between bacteria. The presented model consist of a parabolicparabolic chemotaxis system for the oxygen concentration and the bacteria density coupled to an incompressible Stokes equation for the fluid driven by a gravitational force of the heavier bacteria. We show local existence of weak solutions in a bounded domain in d, d = 2, 3 with no-flux boundary condition and in 2 in the case of inhomogeneous Dirichlet conditions for the oxygen. © 2010 World Scientific Publishing Company.

  18. Dynamics of ellipsoidal tracers in swimming algal suspensions

    Science.gov (United States)

    Yang, Ou; Peng, Yi; Liu, Zhengyang; Tang, Chao; Xu, Xinliang; Cheng, Xiang

    2016-10-01

    Enhanced diffusion of passive tracers immersed in active fluids is a universal feature of active fluids and has been extensively studied in recent years. Similar to microrheology for equilibrium complex fluids, the unusual enhanced particle dynamics reveal intrinsic properties of active fluids. Nevertheless, previous studies have shown that the translational dynamics of spherical tracers are qualitatively similar, independent of whether active particles are pushers or pullers—the two fundamental classes of active fluids. Is it possible to distinguish pushers from pullers by simply imaging the dynamics of passive tracers? Here, we investigated the diffusion of isolated ellipsoids in algal C. reinhardtii suspensions—a model for puller-type active fluids. In combination with our previous results on pusher-type E. coli suspensions [Peng et al., Phys. Rev. Lett. 116, 068303 (2016), 10.1103/PhysRevLett.116.068303], we showed that the dynamics of asymmetric tracers show a profound difference in pushers and pullers due to their rotational degree of freedom. Although the laboratory-frame translation and rotation of ellipsoids are enhanced in both pushers and pullers, similar to spherical tracers, the anisotropic diffusion in the body frame of ellipsoids shows opposite trends in the two classes of active fluids. An ellipsoid diffuses fastest along its major axis when immersed in pullers, whereas it diffuses slowest along the major axis in pushers. This striking difference can be qualitatively explained using a simple hydrodynamic model. In addition, our study on algal suspensions reveals that the influence of the near-field advection of algal swimming flows on the translation and rotation of ellipsoids shows different ranges and strengths. Our work provides not only new insights into universal organizing principles of active fluids, but also a convenient tool for detecting the class of active particles.

  19. Friction factors of colloidal suspension containing silicon dioxide nanoparticles in water

    Science.gov (United States)

    Tang, Clement; Pant, Sarbottam; Sharif, Md. Tanveer

    2015-11-01

    The purpose of this study is to experimentally characterize the friction factor of a colloidal suspension flow in circular and square tubes. The suspension contained silicon dioxide nanoparticles dispersed in distilled water at 9.58% volume concentration. Rheological measurements indicated that the suspension exhibits non-Newtonian behavior, and could be modelled as a power-law generalized Newtonian fluid. The experimental study showed that, with proper characterization of the consistency and flow behavior indices, the suspension flow friction factors in circular and square tubes exhibit similarities with those of Newtonian fluid flow. In the laminar fully-developed flow region, the Poiseuille numbers are similar to those established for Newtonian fluid flow. In the turbulent region, the Dodge and Metzner relation between the friction factor and a generalized Reynolds number can adequately describe the flow. The onsets of transition to turbulent flow for the suspension vary with the shape of the tube and differ from those of Newtonian fluid flow. The deviations suggest that the flow passage shape and the presence of nanoparticles affect the onset of transition to turbulent flow. Supported by North Dakota NASA EPSCoR.

  20. Emergence of coherent structures and large-scale flows in motile suspensions.

    Science.gov (United States)

    Saintillan, David; Shelley, Michael J

    2012-03-01

    The emergence of coherent structures, large-scale flows and correlated dynamics in suspensions of motile particles such as swimming micro-organisms or artificial microswimmers is studied using direct particle simulations. A detailed model is proposed for a slender rod-like particle that propels itself in a viscous fluid by exerting a prescribed tangential stress on its surface, and a method is devised for the efficient calculation of hydrodynamic interactions in large-scale suspensions of such particles using slender-body theory and a smooth particle-mesh Ewald algorithm. Simulations are performed with periodic boundary conditions for various system sizes and suspension volume fractions, and demonstrate a transition to large-scale correlated motions in suspensions of rear-actuated swimmers, or Pushers, above a critical volume fraction or system size. This transition, which is not observed in suspensions of head-actuated swimmers, or Pullers, is seen most clearly in particle velocity and passive tracer statistics. These observations are consistent with predictions from our previous mean-field kinetic theory, one of which states that instabilities will arise in uniform isotropic suspensions of Pushers when the product of the linear system size with the suspension volume fraction exceeds a given threshold. We also find that the collective dynamics of Pushers result in giant number fluctuations, local alignment of swimmers and strongly mixing flows. Suspensions of Pullers, which evince no large-scale dynamics, nonetheless display interesting deviations from the random isotropic state.

  1. Settling of isolated particles and of suspensions in a shear-thinning medium; Sedimentation de particules isolees et de suspensions en milieu rheofluidifiant

    Energy Technology Data Exchange (ETDEWEB)

    Daugan, S.

    2002-11-01

    After drawing up a balance sheet of current knowledge of settling of particles and suspensions in Newtonian and non Newtonian fluids, we introduce the characterisation of the fluid-particles system and especially the shear-thinning behavior of Xanthan solutions. This experimental study is organised into two parts. First of all, we study the settling behavior of a few particles falling along their line of centres. The conditions for particles aggregation with respect to the rheological properties of the suspending fluid are systematically reported. To that extent, rheological relaxation experiments are performed. Once aggregated, the particles velocities are much more important that the velocity of a single one. We show that a simple model, based on the Newtonian case, allows to predict the position and the velocity of each particle with respect to the initial separation distance between them. The second part of this work is devoted to the study of the settling behavior of spherical and monodisperse particles suspensions according to the particles volume fraction, the polymer concentration of the suspending fluid and the geometry of the sedimenting cell. From a model giving the particle volume fraction as a function of the luminous intensity transmitted by the suspension, we show that three regimes of different kinetics occur. During the second regime, the particle volume fraction decreases exponentially with time and the observed phenomena are very fast. Finally, we study the spatial structuration of the suspension and we link it to the topography of the sediment obtained at the end of the sedimentation. (author)

  2. Particle-based simulations of self-motile suspensions

    Science.gov (United States)

    Hinz, Denis F.; Panchenko, Alexander; Kim, Tae-Yeon; Fried, Eliot

    2015-11-01

    A simple model for simulating flows of active suspensions is investigated. The approach is based on dissipative particle dynamics. While the model is potentially applicable to a wide range of self-propelled particle systems, the specific class of self-motile bacterial suspensions is considered as a modeling scenario. To mimic the rod-like geometry of a bacterium, two dissipative particle dynamics particles are connected by a stiff harmonic spring to form an aggregate dissipative particle dynamics molecule. Bacterial motility is modeled through a constant self-propulsion force applied along the axis of each such aggregate molecule. The model accounts for hydrodynamic interactions between self-propelled agents through the pairwise dissipative interactions conventional to dissipative particle dynamics. Numerical simulations are performed using a customized version of the open-source software package LAMMPS (Large-scale Atomic/Molecular Massively Parallel Simulator) software package. Detailed studies of the influence of agent concentration, pairwise dissipative interactions, and Stokes friction on the statistics of the system are provided. The simulations are used to explore the influence of hydrodynamic interactions in active suspensions. For high agent concentrations in combination with dominating pairwise dissipative forces, strongly correlated motion patterns and a fluid-like spectral distributions of kinetic energy are found. In contrast, systems dominated by Stokes friction exhibit weaker spatial correlations of the velocity field. These results indicate that hydrodynamic interactions may play an important role in the formation of spatially extended structures in active suspensions.

  3. An investigation of particles suspension using smoothed particle hydrodynamics

    Science.gov (United States)

    Pazouki, Arman; Negrut, Dan

    2013-11-01

    This contribution outlines a method for the direct numerical simulation of rigid body suspensions in a Lagrangian-Lagrangian framework using extended Smoothed Particle Hydrodynamics (XSPH) method. The dynamics of the arbitrarily shaped rigid bodies is fully resolved via Boundary Condition Enforcing (BCE) markers and updated according to the general Newton-Euler equations of motion. The simulation tool, refered to herien as Chrono::Fluid, relies on a parallel implementation that runs on Graphics Processing Unit (GPU) cards. The simulation results obtained for transient Poiseuille flow, migration of cylinder and sphere in Poiseuille flow, and distribution of particles at different cross sections of the laminar flow of dilute suspension were respectively within 0.1%, 1%, and 5% confidence interval of analytical and experimental results reported in the literature. It was shown that at low Reynolds number, Re = O(1), the radial migration (a) behaves non-monotonically as the particles relative distance (distance over diameter) increases from zero to two; and (b) decreases as the particle skewness and size increases. The scaling of Chrono::Fluid was demonstrated in conjunction with a suspension dynamics analysis in which the number of ellipsoids went up to 3e4. Financial support was provided in part by National Science Foundation grant NSF CMMI-084044.

  4. Control of quadriaxial cardan suspension

    Science.gov (United States)

    Novozhilov, I. V.

    1984-04-01

    A quadriaxial Cardan suspension is to be servomechanically controlled so as to stabilize a definite orientation of the platform during arbitrary motion of the frame. The problem is solved with the use of five orthogonal systems of coordinates tied one to the platform, one to each of the three gimbals, and one to the frame respectively. The suspension is assumed to be structurally perfectly rigid and to be part of a gyroscopic indicator-stabilization system. The corresponding dynamic equations are written as equations for angular momenta and several variants of control, for the various rotations, are constructed. One such variant, a more intricate one, is course-vertical control. Dynamic control of the suspension in a stationary frame, to ensure any arbitrarily prescribed angular evolutions of the platform, is also considered and the procedure for constructing such a control is outlined.

  5. Experimental Investigation and Optimization of Solid Suspension in Non-Newtonian Liquids at High Solid Concentration

    Directory of Open Access Journals (Sweden)

    Roozbeh Mollaabbasi

    2016-01-01

    Full Text Available This research deals with experimental work on solid suspension and dispersion in stirred tank reactors that operate with complex fluids. Only suspended speed (Njs throughout the vessel was characterized using Gamma-Ray Densitometry. The outcomes of this study help to understand solid suspension mechanisms involving changes the rheology of the fluid and provide engineering data for designing stirred tanks. All experiments were based on classic radial and axial flow impellers, i.e., Rushton Turbine (RT and Pitched Blade Turbine in down pumping mode (PBT-D. Three different liquids (water, water+CMC, and water+PAA were employed in several concentrations. The CMC solution introduced as a pseudo plastic fluid and PAA solution was applied as a Herschel Bulkley fluid. The rheological properties of these fluids were characterized separately. According to the findings, the critical impeller speeds for solid suspension for non-Newtonian fluids were more eminent than those for water. Experiments were performed to characterize the effects of solid loading, impeller clearance and viscosity on Njs. Also the PSO method is employed to find suitable parameters of Zwietering's correlation for prediction of Njs in Non Newtonian fluids.

  6. 摩托车

    Institute of Scientific and Technical Information of China (English)

    2005-01-01

    A magneto-rheological fluid shock absorber for an off-road motorcycle, A multibody code for motorcycle handling and stability analysis with validation and examples of application, A parallel hybrid powertrain for a motorcycle application, A study of LPG lean burn for a small SI engine,A study on motorcycle-rider system simulations。

  7. Active Control of Suspension Bridges

    DEFF Research Database (Denmark)

    Thoft-Christensen, Palle

    In this paper some recent research on active control of very long suspension bridges, is presented. The presentation is based on research work at Aalborg University, Denmark. The active control system is based on movable flaps attached to the bridge girder. Wind load on bridges with or without...... flaps attached to the girder is briefly presented. A simple active control system is discussed. Results from wind tunnel experiments with a bridge section show that flaps can be used effectively to control bridge girder vibrations. Flutter conditions for suspension bridges with and without flaps...

  8. Detection of CDH1 gene methylation of suspension cells in abdominal lavage fluid from colorectal cancer patients and its clinical significance%结直肠癌术中腹腔灌洗液悬浮细胞CDH1甲基化检测及其临床意义

    Institute of Scientific and Technical Information of China (English)

    鲁发龙; 杜刚毅; 郑少康; 彭林; 陈金泉

    2014-01-01

    目的 检测结直肠癌术中腹腔灌洗液悬浮细胞中CDH1基因甲基化状态并探讨其与结直肠癌临床病理资料及预后的关系.方法 前瞻性纳入2011年10月至2013年10月间中山市中医院手术治疗的原发性结直肠癌患者.采用实时荧光甲基化特异性聚合酶链反应技术,检测术中腹腔灌洗液悬浮细胞中CDH1基因启动子区域5'-CpG岛的甲基化状态,将甲基化百分率大于20%定义为甲基化,小于或等于20%为非甲基化;分析CDH1基因甲基化状态与结直肠癌临床病理特征及预后的关系.结果 共102例患者纳入研究,其中CDH1甲基化组47例,非甲基化组55例.与非甲基化组比较,甲基化组患者肿瘤直径更大,浸润型比例更高,分化程度更低,淋巴结转移和远处转移率更高,临床分期更晚(均P<0.05).甲基化组患者中位生存期短于非甲基化组(26.0月比41.4月,P<0.05).Cox模型分析显示,CDH1甲基化状态是结直肠癌患者术后生存的独立危险因素(RR=27.5,95%CI:3.8~51.3,P<0.01].结论 术中腹腔灌洗液悬浮细胞中CDH1基因发生甲基化的结直肠癌患者恶性程度较高,易发生淋巴结转移和远处转移,预后较差.%Objective To detect the CDH1 gene methylation of suspension cells in intraoperative abdominal lavage fluid from colorectal cancer patients,and to examine its association with clinicopathology and prognosis.Methods Real-time methylation-specific polymerase chain reaction (qMSP) was used to investigate the methylation status of the CDH 1 gene promoter 5'-CpG islands from intraoperative abdominal lavage fluid in 102 patients with colorectal cancer.The associations between methylation of CDH1 genes and clinicopathologic features and prognosis were investigated.Results Among the 102 colorectal cancer patients,aberrant methylation of CDH1 gene was detected in 47 patients.Significant associations were found between CDH1 methylation status and tumor size,growth pattern

  9. Apparent slip at the surface of a ball spinning in a concentrated suspension.

    Energy Technology Data Exchange (ETDEWEB)

    Brenner, Howard H. (Massachusetts Institute of Technology, Cambridge, MA); Graham, Alan Lyman (Los Alamos National Laboratory, Los Alamos, NM); Grillet, Anne Mary; Pacheco, Glynis; Ingber, Marc Stuart (University of New Mexico, Albuquerque, NM); Mondy, Lisa Ann; Henfling, John Francis

    2004-06-01

    The couple on a ball rotating relative to an otherwise quiescent suspension of comparably-sized, neutrally buoyant spheres is studied both experimentally and numerically. Apparent 'slip' relative to the analytical solution for a sphere spinning in a Newtonian fluid (based upon the viscosity of the suspension) is determined in suspensions with volume fractions c ranging from 0.03 to 0.50. This apparent slip results in a decrease of the measured torque on the spinning ball when the radius of the ball becomes comparable with that of the suspended spheres. Over the range of our data, the slip becomes more pronounced as the concentration c increases. At c = 0.25, three-dimensional boundary-element simulations agree well with the experimental data. Moreover, at c = 0.03, good agreement exists between such calculations and theoretical predictions of rotary slip in dilute suspensions.

  10. A New Device for Characterisation of the Drainage Kinetics of Fibrous Suspensions Under Gravity

    Directory of Open Access Journals (Sweden)

    Przybysz Piotr

    2014-12-01

    Full Text Available Gravity dewatering of fibrous suspension is one of basic technological operations in paper production process. Although there are numerous methods to determine dewatering of such suspensions, none of them can measure undisturbed flow of removed water. In the paper the idea and design of a new apparatus for the determination of drainage rate of fibrous suspensions is presented. The apparatus differs from other known devices by minimisation of filtrate flow resistance in the outlet part of the equipment. In the second part of the paper measurements of the drainage rate have been presented. The flow resistance of the fluid through the bottom wire screen in the device was determined. The calculated flow resistance will be used in the developed model of dynamic drainage of fibrous suspensions, which will be discussed in our following paper (Przybysz et al., 2014.

  11. Producing a highly concentrated coal suspension

    Energy Technology Data Exchange (ETDEWEB)

    Mokudzu, K.; Atsudzima, T.; Kiyedzuka, Y.

    1983-06-03

    Coal from wet and dry grinding is loaded into a mixer with a mixer arm with the acquisition of a highly concentrated suspension. Foamers (for instance, alkylbenzolsulfonate) and foam stabilizers (for instance diethanolamide of lauric acid) are added in a ratio of 10 to (2 to 5). The high fluidity of the suspension is maintained by injecting air into the suspension and an 80 percent concentration of the suspension is achieved.

  12. Rheology and structural arrest of casein suspensions

    OpenAIRE

    Dahbi, Louisa; Alexander, M.; Trappe, Véronique; Dhont, J. K. G.; Schurtenberger, Peter

    2010-01-01

    The rheology of milk powder suspensions is investigated up to very high concentrations, where structural arrest occurs. The main component of the milk powder investigated is casein, so that the suspensions can be regarded as casein suspensions. Four concentration regimes are identified. For effective casein volume fractions less than 0.54 the concentration dependence of the zero-shear viscosity is similar to that of hard-sphere suspensions. However, due to the elastic deformation of the casei...

  13. Adaptive magnetorheological seat suspension for shock mitigation

    Science.gov (United States)

    Singh, Harinder Jit

    This research focuses on theoretical and experimental analysis of an adaptive seat suspension employing magnetorheological energy absorber with the objective of minimizing injury potential to seated occupant of different weights subjected to broader crash intensities. The research was segmented into three tasks: (1) development of magnetorheological energy absorber, (2) biodynamic modeling of a seated occupant, and (3) control schemes for shock mitigation. A linear stroking semi-active magnetorheological energy absorber (MREA) was designed, fabricated and tested for intense impact conditions with piston velocities up to 8 m/s. MREA design was optimized on the basis of Bingham-plastic model (BPM model) in order to maximize the energy absorption capabilities at high impact velocities. Computational fluid dynamics and magnetic FE analysis were conducted to validate MREA performance. Subsequently, low-speed cyclic testing (0-2 Hz subjected to 0-5.5 A) and high-speed drop testing (0-4.5 m/s at 0 A) were conducted for quantitative comparison with the numerical simulations. Later, a nonlinear four degrees-of-freedom biodynamic model representing a seated 50th percentile male occupant was developed on the basis of experiments conducted on Hybrid II 50th percentile male anthropomorphic test device. The response of proposed biodynamic model was compared quantitatively against two different biodynamic models from the literature that are heavily implemented for obtaining biodynamic response under impact conditions. The proposed biodynamic model accurately predicts peak magnitude, overall shape and the duration of the biodynamic transient response, with minimal phase shift. The biodynamic model was further validated against 16 impact tests conducted on horizontal accelerator facility at NAVAIR for two different shock intensities. Compliance effects of human body were also investigated on the performance of adaptive seat suspension by comparing the proposed biodynamic model

  14. Dynamics of the colloidal suspensions

    Institute of Scientific and Technical Information of China (English)

    ZHANG Hai-yan; MA Hong-ru

    2006-01-01

    This article offers a survey on our current knowledge of the dynamics of the colloidal suspension,where each particle experiences the friction force with solvent,hydrodynamic interaction,and potential force from surrounding particles and thermodynamic force.It further contains a summary of the basic concepts about microstructures and equilibrium properties,and of analytical and numerical methods,which are relevant for the theoretical description of the suspensions.The description of the dynamics of colloidal particles,based on the generalized Smoluchowski equation,is justified for the time scale accessible in DLS experiments.The combined influence of hard sphere or electrostatic potential and solvent-mediated hydrodynamic interaction on the short-time dynamics of monodisperse suspensions is investigated in detail.A thorough study of tracer-diffusion in hard sphere and charge-stabilized suspensions is presented.Mean-square displacements and long-time tracer-diffusion coefficients are calculated with two alternative approximations,i.e.,a mode-coupling scheme and a single relaxation time ansatz.

  15. Suspension-Firing of Biomass

    DEFF Research Database (Denmark)

    Shafique Bashir, Muhammad; Jensen, Peter Arendt; Frandsen, Flemming

    2012-01-01

    This paper is the second of two papers, describing probe measurements of deposit buildup and removal (shedding), conducted in a 350 MWth suspension-fired boiler, firing straw and wood. Investigations of deposit buildup and shedding have been made by use of an advanced online deposit probe and a s...

  16. Fluid Mechanics.

    Science.gov (United States)

    Drazin, Philip

    1987-01-01

    Outlines the contents of Volume II of "Principia" by Sir Isaac Newton. Reviews the contributions of subsequent scientists to the physics of fluid dynamics. Discusses the treatment of fluid mechanics in physics curricula. Highlights a few of the problems of modern research in fluid dynamics. Shows that problems still remain. (CW)

  17. Fluid Interfaces

    DEFF Research Database (Denmark)

    Hansen, Klaus Marius

    2001-01-01

    Fluid interaction, interaction by the user with the system that causes few breakdowns, is essential to many user interfaces. We present two concrete software systems that try to support fluid interaction for different work practices. Furthermore, we present specificity, generality, and minimality...... as design goals for fluid interfaces....

  18. Fluid Mechanics.

    Science.gov (United States)

    Drazin, Philip

    1987-01-01

    Outlines the contents of Volume II of "Principia" by Sir Isaac Newton. Reviews the contributions of subsequent scientists to the physics of fluid dynamics. Discusses the treatment of fluid mechanics in physics curricula. Highlights a few of the problems of modern research in fluid dynamics. Shows that problems still remain. (CW)

  19. 7 CFR 3015.123 - Suspension.

    Science.gov (United States)

    2010-01-01

    ... 7 Agriculture 15 2010-01-01 2010-01-01 false Suspension. 3015.123 Section 3015.123 Agriculture... AGRICULTURE UNIFORM FEDERAL ASSISTANCE REGULATIONS Grant and Subgrant Closeout, Suspension and Termination § 3015.123 Suspension. (a) When a recipient has materially failed to comply with the...

  20. 36 CFR 1212.670 - Suspension.

    Science.gov (United States)

    2010-07-01

    ... 36 Parks, Forests, and Public Property 3 2010-07-01 2010-07-01 false Suspension. 1212.670 Section... GOVERNMENTWIDE REQUIREMENTS FOR DRUG-FREE WORKPLACE (FINANCIAL ASSISTANCE) Definitions § 1212.670 Suspension. Suspension means an action taken by a Federal agency that immediately prohibits a recipient...

  1. 48 CFR 609.407 - Suspension.

    Science.gov (United States)

    2010-10-01

    ... 48 Federal Acquisition Regulations System 4 2010-10-01 2010-10-01 false Suspension. 609.407 Section 609.407 Federal Acquisition Regulations System DEPARTMENT OF STATE COMPETITION AND ACQUISITION PLANNING CONTRACTOR QUALIFICATIONS Debarment, Suspension, and Ineligibility 609.407 Suspension....

  2. 48 CFR 1409.407 - Suspension.

    Science.gov (United States)

    2010-10-01

    ... 48 Federal Acquisition Regulations System 5 2010-10-01 2010-10-01 false Suspension. 1409.407 Section 1409.407 Federal Acquisition Regulations System DEPARTMENT OF THE INTERIOR COMPETITION AND ACQUISITION PLANNING CONTRACTOR QUALIFICATIONS Debarment, Suspension, and Ineligibility 1409.407 Suspension....

  3. 25 CFR 23.52 - Grant suspension.

    Science.gov (United States)

    2010-04-01

    ... 25 Indians 1 2010-04-01 2010-04-01 false Grant suspension. 23.52 Section 23.52 Indians BUREAU OF... Grant Administration Provisions and Requirements § 23.52 Grant suspension. (a) When a grantee has... assistance, suspend the grant. The notice preceding the suspension shall include the effective date of...

  4. 36 CFR 223.141 - Suspension.

    Science.gov (United States)

    2010-07-01

    ... 36 Parks, Forests, and Public Property 2 2010-07-01 2010-07-01 false Suspension. 223.141 Section... DISPOSAL OF NATIONAL FOREST SYSTEM TIMBER Suspension and Debarment of Timber Purchasers § 223.141 Suspension. (a) The suspending official may, in the public interest, suspend a purchaser on the basis...

  5. 32 CFR 552.79 - Suspension action.

    Science.gov (United States)

    2010-07-01

    ... 32 National Defense 3 2010-07-01 2010-07-01 true Suspension action. 552.79 Section 552.79 National... Suspension action. (a) When suspended for cause, immediately notify the company and the agent, in writing, of the reason. When the installation commander determines that suspension should be extended...

  6. 41 CFR 105-74.670 - Suspension.

    Science.gov (United States)

    2010-07-01

    ... 41 Public Contracts and Property Management 3 2010-07-01 2010-07-01 false Suspension. 105-74.670...-GOVERNMENTWIDE REQUIREMENTS FOR DRUG-FREE WORKPLACE (FINANCIAL ASSISTANCE) Definitions § 105-74.670 Suspension. Suspension means an action taken by a Federal agency that immediately prohibits a recipient...

  7. 21 CFR 520.1640 - Oxibendazole suspension.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 6 2010-04-01 2010-04-01 false Oxibendazole suspension. 520.1640 Section 520.1640... DRUGS, FEEDS, AND RELATED PRODUCTS ORAL DOSAGE FORM NEW ANIMAL DRUGS § 520.1640 Oxibendazole suspension. (a) Specifications. The suspension contains 10 percent oxibendazole. (b) Sponsor. See 000069 in §...

  8. 45 CFR 1210.3-3 - Suspension.

    Science.gov (United States)

    2010-10-01

    ... 45 Public Welfare 4 2010-10-01 2010-10-01 false Suspension. 1210.3-3 Section 1210.3-3 Public... § 1210.3-3 Suspension. (a) The ACTION State Director may suspend a Volunteer for up to 30 days in order... Volunteer. Suspension is not warranted if the State Director determines that sufficient grounds...

  9. 21 CFR 26.16 - Suspension.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 1 2010-04-01 2010-04-01 false Suspension. 26.16 Section 26.16 Food and Drugs... Provisions for Pharmaceutical Good Manufacturing Practices § 26.16 Suspension. (a) Each party has the right... after such notification, the contested authority will be suspended. (d) Upon the suspension of...

  10. 32 CFR 776.82 - Interim suspension.

    Science.gov (United States)

    2010-07-01

    ... 32 National Defense 5 2010-07-01 2010-07-01 false Interim suspension. 776.82 Section 776.82... Complaint Processing Procedures § 776.82 Interim suspension. (a) Where the Rules Counsel determines there is... interim suspension, pending completion of a professional responsibility investigation. The...

  11. 49 CFR 393.207 - Suspension systems.

    Science.gov (United States)

    2010-10-01

    ... 49 Transportation 5 2010-10-01 2010-10-01 false Suspension systems. 393.207 Section 393.207... NECESSARY FOR SAFE OPERATION Frames, Cab and Body Components, Wheels, Steering, and Suspension Systems § 393.207 Suspension systems. (a) Axles. No axle positioning part shall be cracked, broken, loose or...

  12. 75 FR 24494 - Nonprocurement Debarment and Suspension

    Science.gov (United States)

    2010-05-05

    ...; ] ELECTION ASSISTANCE COMMISSION 2 CFR Chapter 58 Nonprocurement Debarment and Suspension AGENCY: U.S... proposed debarment and suspension regulations. These proposed regulations will apply to nonprocurement... Management and Budget (OMB) in a document on nonprocurement debarment and suspension published in the...

  13. 48 CFR 509.407 - Suspension.

    Science.gov (United States)

    2010-10-01

    ... 48 Federal Acquisition Regulations System 4 2010-10-01 2010-10-01 false Suspension. 509.407 Section 509.407 Federal Acquisition Regulations System GENERAL SERVICES ADMINISTRATION COMPETITION AND ACQUISITION PLANNING CONTRACTOR QUALIFICATIONS Debarment, Suspension, and Ineligibility 509.407 Suspension....

  14. 48 CFR 2009.407 - Suspension.

    Science.gov (United States)

    2010-10-01

    ... 48 Federal Acquisition Regulations System 6 2010-10-01 2010-10-01 true Suspension. 2009.407 Section 2009.407 Federal Acquisition Regulations System NUCLEAR REGULATORY COMMISSION COMPETITION AND ACQUISITION PLANNING CONTRACTOR QUALIFICATIONS Debarment, Suspension, and Ineligibility 2009.407 Suspension....

  15. 21 CFR 522.1289 - Lufenuron suspension.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 6 2010-04-01 2010-04-01 false Lufenuron suspension. 522.1289 Section 522.1289 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) ANIMAL... Lufenuron suspension. (a) Specifications. Each milliliter of sterile aqueous suspension contains...

  16. 32 CFR 552.80 - Suspension period.

    Science.gov (United States)

    2010-07-01

    ... 32 National Defense 3 2010-07-01 2010-07-01 true Suspension period. 552.80 Section 552.80 National... Suspension period. All solicitation privileges suspended by installation commanders will be for a specific time. Normally, it will not exceed 2 years. When the suspension period expires, the agent may...

  17. 48 CFR 409.407 - Suspension.

    Science.gov (United States)

    2010-10-01

    ... 48 Federal Acquisition Regulations System 4 2010-10-01 2010-10-01 false Suspension. 409.407 Section 409.407 Federal Acquisition Regulations System DEPARTMENT OF AGRICULTURE COMPETITION AND ACQUISITION PLANNING CONTRACTOR QUALIFICATIONS Debarment, Suspension and Ineligibility 409.407 Suspension....

  18. 22 CFR 127.8 - Interim suspension.

    Science.gov (United States)

    2010-04-01

    ... 22 Foreign Relations 1 2010-04-01 2010-04-01 false Interim suspension. 127.8 Section 127.8 Foreign... Interim suspension. (a) The Managing Director of the Directorate of Defense Trade Controls or the Director of the Office of Defense Trade Controls Compliance is authorized to order the interim suspension...

  19. 40 CFR 36.670 - Suspension.

    Science.gov (United States)

    2010-07-01

    ... 40 Protection of Environment 1 2010-07-01 2010-07-01 false Suspension. 36.670 Section 36.670... REQUIREMENTS FOR DRUG-FREE WORKPLACE (FINANCIAL ASSISTANCE) Definitions § 36.670 Suspension. Suspension means... contracts (48 CFR part 9, subpart 9.4) and the common rule, Government-wide Debarment and...

  20. 38 CFR 48.670 - Suspension.

    Science.gov (United States)

    2010-07-01

    ... 38 Pensions, Bonuses, and Veterans' Relief 2 2010-07-01 2010-07-01 false Suspension. 48.670...) GOVERNMENTWIDE REQUIREMENTS FOR DRUG-FREE WORKPLACE (FINANCIAL ASSISTANCE) Definitions § 48.670 Suspension. Suspension means an action taken by a Federal agency that immediately prohibits a recipient...

  1. 32 CFR 26.670 - Suspension.

    Science.gov (United States)

    2010-07-01

    ... 32 National Defense 1 2010-07-01 2010-07-01 false Suspension. 26.670 Section 26.670 National... GOVERNMENTWIDE REQUIREMENTS FOR DRUG-FREE WORKPLACE (FINANCIAL ASSISTANCE) Definitions § 26.670 Suspension. Suspension means an action taken by a Federal agency that immediately prohibits a recipient...

  2. 25 CFR 558.5 - License suspension.

    Science.gov (United States)

    2010-04-01

    ... 25 Indians 2 2010-04-01 2010-04-01 false License suspension. 558.5 Section 558.5 Indians NATIONAL... MANAGEMENT OFFICIALS § 558.5 License suspension. (a) If, after the issuance of a gaming license, the... tribe shall suspend such license and shall notify in writing the licensee of the suspension and...

  3. 48 CFR 9.407 - Suspension.

    Science.gov (United States)

    2010-10-01

    ... 48 Federal Acquisition Regulations System 1 2010-10-01 2010-10-01 false Suspension. 9.407 Section 9.407 Federal Acquisition Regulations System FEDERAL ACQUISITION REGULATION ACQUISITION PLANNING CONTRACTOR QUALIFICATIONS Debarment, Suspension, and Ineligibility 9.407 Suspension....

  4. 22 CFR 34.20 - Suspension.

    Science.gov (United States)

    2010-04-01

    ... 22 Foreign Relations 1 2010-04-01 2010-04-01 false Suspension. 34.20 Section 34.20 Foreign Relations DEPARTMENT OF STATE CLAIMS AND STOLEN PROPERTY DEBT COLLECTION Collection Adjustments § 34.20 Suspension. The suspension of collection action shall be made in accordance with the standards set forth...

  5. 48 CFR 909.407 - Suspension.

    Science.gov (United States)

    2010-10-01

    ... 48 Federal Acquisition Regulations System 5 2010-10-01 2010-10-01 false Suspension. 909.407 Section 909.407 Federal Acquisition Regulations System DEPARTMENT OF ENERGY COMPETITION ACQUISITION PLANNING CONTRACTOR QUALIFICATIONS Debarment, Suspension, and Ineligibility 909.407 Suspension....

  6. 48 CFR 2509.407 - Suspension.

    Science.gov (United States)

    2010-10-01

    ... 48 Federal Acquisition Regulations System 6 2010-10-01 2010-10-01 true Suspension. 2509.407 Section 2509.407 Federal Acquisition Regulations System NATIONAL SCIENCE FOUNDATION ACQUISITION PLANNING CONTRACTOR QUALIFICATIONS Debarment, Suspension, and Ineligibility 2509.407 Suspension....

  7. 48 CFR 309.407 - Suspension.

    Science.gov (United States)

    2010-10-01

    ... 48 Federal Acquisition Regulations System 4 2010-10-01 2010-10-01 false Suspension. 309.407 Section 309.407 Federal Acquisition Regulations System HEALTH AND HUMAN SERVICES COMPETITION AND ACQUISITION PLANNING CONTRACTOR QUALIFICATIONS Debarment, Suspension, and Ineligibility 309.407 Suspension....

  8. 21 CFR 520.1806 - Piperazine suspension.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 6 2010-04-01 2010-04-01 false Piperazine suspension. 520.1806 Section 520.1806... DRUGS, FEEDS, AND RELATED PRODUCTS ORAL DOSAGE FORM NEW ANIMAL DRUGS § 520.1806 Piperazine suspension. (a) Specifications. Each milliliter of suspension contains piperazine monohydrochloride equivalent...

  9. 48 CFR 809.407 - Suspension.

    Science.gov (United States)

    2010-10-01

    ... 48 Federal Acquisition Regulations System 5 2010-10-01 2010-10-01 false Suspension. 809.407 Section 809.407 Federal Acquisition Regulations System DEPARTMENT OF VETERANS AFFAIRS COMPETITION AND ACQUISITION PLANNING CONTRACTOR QUALIFICATIONS Debarment, Suspension, and Ineligibility 809.407 Suspension....

  10. 48 CFR 1509.407 - Suspension.

    Science.gov (United States)

    2010-10-01

    ... 48 Federal Acquisition Regulations System 6 2010-10-01 2010-10-01 true Suspension. 1509.407 Section 1509.407 Federal Acquisition Regulations System ENVIRONMENTAL PROTECTION AGENCY ACQUISITION PLANNING CONTRACTOR QUALIFICATIONS Debarment, Suspension and Ineligibility 1509.407 Suspension....

  11. 48 CFR 1309.407 - Suspension.

    Science.gov (United States)

    2010-10-01

    ... 48 Federal Acquisition Regulations System 5 2010-10-01 2010-10-01 false Suspension. 1309.407 Section 1309.407 Federal Acquisition Regulations System DEPARTMENT OF COMMERCE COMPETITION AND ACQUISITION PLANNING CONTRACTOR QUALIFICATIONS Debarment, Suspension, and Ineligibility 1309.407 Suspension....

  12. 34 CFR 682.705 - Suspension proceedings.

    Science.gov (United States)

    2010-07-01

    ... 34 Education 3 2010-07-01 2010-07-01 false Suspension proceedings. 682.705 Section 682.705....705 Suspension proceedings. (a) Scope. (1) A suspension by the Secretary removes a lender's... limitation or a termination proceeding. (2) If the Secretary begins a limitation or a termination...

  13. 34 CFR 668.85 - Suspension proceedings.

    Science.gov (United States)

    2010-07-01

    ... 34 Education 3 2010-07-01 2010-07-01 false Suspension proceedings. 668.85 Section 668.85 Education... Proceedings § 668.85 Suspension proceedings. (a) Scope and consequences. (1) The Secretary may suspend an... a suspension proceeding against a third-party servicer, the Secretary also may begin a...

  14. Computational model of interacting suspensions at low Reynolds number in the presence of external fields

    Science.gov (United States)

    Wang, Zhou Joseph

    2001-08-01

    This dissertation concentrates on developing and implementing models to predict the motion of rigid suspensions immersed in a viscous fluid. The spheres are subjected to prescribed forces, torques or an imposed linear shear flow. Hydrodynamic as well as electrostatic interactions between the suspensions is investigated. Analytical models are developed for binary interactions in an N-body simulation. Green's functions of Stokes equation, integrated over the surface of the spheres and the boundary patches are utilized to derive these binary interactions. The method accurately accounts for both near-field lubrication and multi-body interactions. A method of boundary effects in sheared concentrated suspensions is implemented to simulate the suspension of spheres confined between two plane walls that translate relative to one another. Periodic boundary conditions are imposed in the stream-wise direction to simulate an infinite suspension. Using linear superposition of forces, it is then possible to derive the net force acting on each particle due to its interaction with all other particles in the suspension via hydrodynamic forces propagated through the fluid medium, and the interaction with the boundaries. The electrostatic effects are added to the hydrodynamic effects to produce a more faithful simulation of electro- rheological effects. In order to consider multipole and multi-body effects of electro-rheological interactions, a method is implemented that relates the charge and dipole moments of the particles to their potentials and the applied electric field. This method includes both the multi-body far-field and near-field particle interactions and properly accounts for the long-range interactions. Coupled with multi-body hydrodynamics interactions of the particles, the dynamics of the microstructure and its rheological properties can be determined. A series of simulations are conducted to understand the effect of water, concentration of suspensions, electric field

  15. Review of magnetorheological (MR) fluids and its applications in vibration control

    Institute of Scientific and Technical Information of China (English)

    MUHAMMAD Aslam; YAO Xiong-liang; DENG Zhong-chao

    2006-01-01

    Magnetorheological (MR) fluids are now well established as one of the leading materials for use in controllable structures and systems. Commercial application of MR fluids in various fields,particularly in the vibration control, has grown rapidly over the past few years. In this paper, properties of magnetorheological (MR) fluids ,its applications in suspensions of vehicles, suspension of trains, high buildings cable-stayed bridges have been discussed. The scope of MR fluids in future, problems and some suggestions are also presented. Finally, effectiveness of MR fluids in vibration control of marine diesel engine through experiment is briefly discussed by the author.

  16. Characteristics of Students Who Reenroll after Serving a Disciplinary Suspension

    Science.gov (United States)

    Stimpson, Matthew T.; Janosik, Steven M.

    2007-01-01

    The purpose of this study was to examine if students who reenroll following a disciplinary suspension had significant common characteristics. Gender, GPA at time of suspension, class status at time of suspension, type of violation(s) that resulted in suspension, number of disciplinary incidents prior to suspension, and length of suspension were…

  17. Laminar, turbulent, and inertial shear-thickening regimes in channel flow of neutrally buoyant particle suspensions

    NARCIS (Netherlands)

    Lashgari, I.; Picano, F.; Breugem, W.P.; Brandt, L.

    2014-01-01

    The aim of this Letter is to characterize the flow regimes of suspensions of finite-size rigid particles in a viscous fluid at finite inertia. We explore the system behavior as a function of the particle volume fraction and the Reynolds number (the ratio of flow and particle inertia to viscous force

  18. A Colorful Mixing Experiment in a Stirred Tank Using Non-Newtonian Blue Maize Flour Suspensions

    Science.gov (United States)

    Trujilo-de Santiago, Grissel; Rojas-de Gante, Cecillia; García-Lara, Silverio; Ballesca´-Estrada, Adriana; Alvarez, Marion Moise´s

    2014-01-01

    A simple experiment designed to study mixing of a material of complex rheology in a stirred tank is described. Non-Newtonian suspensions of blue maize flour that naturally contain anthocyanins have been chosen as a model fluid. These anthocyanins act as a native, wide spectrum pH indicator exhibiting greenish colors in alkaline environments, blue…

  19. Effect of particle inertia and gravity on the turbulence in a suspension

    NARCIS (Netherlands)

    Ooms, G.; Poesio, P.

    2005-01-01

    A theoretical model is presented for the effect of particle inertia and gravity on the turbulence in a homogeneous suspension. It is an extension of the one-fluid model developed by L’vov, Ooms, and Pomyalov [Phys. Rev. E 67, 046314 (2003)] , in which the effect of gravity was not considered. In the

  20. Fluid fragmentation from hospital toilets

    CERN Document Server

    Traverso, G; Lu, C -C; Maa, R; Langer, R; Bourouiba, L

    2013-01-01

    Hospital-acquired infections represent significant health and financial burdens to society. Clostridium difficile (C. difficile) is a particularly challenging bacteria with the potential to cause severe diarrhea and death. One mode of transmission for C. difficile, as well as other pathogens, which has received little attention is the potential air contamination by pathogen-bearing droplets emanating from toilets. In the fluid dynamics video submitted to the APS DFD Gallery of Fluid Motion 2013, we present flow visualizations via high-speed recordings showing the capture of the product of the fluid fragmentation generated by hospital toilet high-pressure flushes. Important quantities of both large and small droplets are observed. We illustrate how high-pressure flushes and cleaning products currently used in hospital toilets result in aggravating, rather than alleviating, the suspension and recirculation of tenacious airborne pathogen-bearing droplets.

  1. Magnetic movement of biological fluid droplets

    Energy Technology Data Exchange (ETDEWEB)

    Garcia, Antonio A. [Harrington Department of Bioengineering, Arizona State University, Tempe, AZ 85287 (United States)]. E-mail: tony.garcia@asu.edu; Egatz-Gomez, Ana [Harrington Department of Bioengineering, Arizona State University, Tempe, AZ 85287 (United States); Lindsay, Solitaire A. [Harrington Department of Bioengineering, Arizona State University, Tempe, AZ 85287 (United States); Dominguez-Garcia, P. [Departamento de Fisica Fundamental, UNED, Senda del Rey 9, Madrid 28040 (Spain); Melle, Sonia [Harrington Department of Bioengineering, Arizona State University, Tempe, AZ 85287 (United States); Departamento de Optica, Universidad Complutense de Madrid, Arcos de Jalon s/n, Madrid 28037 (Spain); Marquez, Manuel [Harrington Department of Bioengineering, Arizona State University, Tempe, AZ 85287 (United States); Research Center, Philip Morris USA, Richmond, VA 23234 (United States); Rubio, Miguel A. [Departamento de Fisica Fundamental, UNED, Senda del Rey 9, Madrid 28040 (Spain); Picraux, S.T. [Department of Chemical and Materials Engineering, Arizona State University, Tempe, AZ 85287 (United States); Los Alamos National Laboratory, MST-CINT, Los Alamos, NM 87545 (United States); Yang, Dongqing [Department of Chemical and Materials Engineering, Arizona State University, Tempe, AZ 85287 (United States); Aella, P. [Department of Chemical and Materials Engineering, Arizona State University, Tempe, AZ 85287 (United States); Hayes, Mark A. [Department of Chemistry and Biochemistry, Arizona State University, Tempe, AZ 8528 (United States); Gust, Devens [Department of Chemistry and Biochemistry, Arizona State University, Tempe, AZ 8528 (United States); Loyprasert, Suchera [Biodesign Institute, Arizona State University, Tempe, AZ 85287 (United States); Vazquez-Alvarez, Terannie [Biodesign Institute, Arizona State University, Tempe, AZ 85287 (United States); Wang, Joseph [Biodesign Institute, Arizona State University, Tempe, AZ 85287 (United States)

    2007-04-15

    Magnetic fields can be used to control the movement of aqueous drops on non-patterned, silicon nanowire superhydrophobic surfaces. Drops of aqueous and biological fluids are controlled by introducing magnetizable carbonyl iron microparticles into the liquid. Key elements of operations such as movement, coalescence, and splitting of water and biological fluid drops, as well as electrochemical measurement of an analyte are demonstrated. Superhydrophobic surfaces were prepared using vapor-liquid-solid (VLS) growth systems followed by coating with a perfluorinated hydrocarbon molecule. Drops were made from aqueous and biological fluid suspensions with magnetizable microparticle concentrations ranging from 0.1 to 10 wt%.

  2. Rheological Properties of Electrorheological Fluids Beyond and in the Original Transition Zone

    Institute of Scientific and Technical Information of China (English)

    范志康; 梁淑华; 薛旭

    2002-01-01

    We find a nonlinear relationship between the shear stress and shear rate of electrorheological (ER) fluids with aluminosilicate suspension in the original zone corresponding to low shear rates. Beyond the original zone, the ER fluids behave like a Bingham plastic fluid, and their viscosity is nearly constant.

  3. Thermophoresis in colloidal suspensions driven by Marangoni forces.

    Science.gov (United States)

    Würger, Alois

    2007-03-30

    In a hydrodynamic approach to thermophoretic transport in colloidal suspensions, the solute velocity u and the solvent flow v(r) are derived from Stokes' equation, with slip boundary conditions imposed by thermal Marangoni forces. The resulting fluid velocity field v(r) significantly differs from that induced by an externally driven particle. We find, in particular, that thermophoresis due to surface forces is insensitive to hydrodynamic interactions. As a consequence, the thermal diffusion coefficient D(T) of polymer solutions is independent of molecular weight and concentration.

  4. Electric Field-Responsive Mesoporous Suspensions: A Review

    Directory of Open Access Journals (Sweden)

    Seung Hyuk Kwon

    2015-12-01

    Full Text Available This paper briefly reviews the fabrication and electrorheological (ER characteristics of mesoporous materials and their nanocomposites with conducting polymers under an applied electric field when dispersed in an insulating liquid. Smart fluids of electrically-polarizable particles exhibit a reversible and tunable phase transition from a liquid-like to solid-like state in response to an external electric field of various strengths, and have potential applications in a variety of active control systems. The ER properties of these mesoporous suspensions are explained further according to their dielectric spectra in terms of the flow curve, dynamic moduli, and yield stress.

  5. Numerical study of hydrodynamic interactions and ordering in a 2-D micro-suspension of active agents

    CERN Document Server

    Behmadi, Hojjat; Najafi, Ali

    2016-01-01

    Ordering in a 2-dimensional active micro-suspension is a challenging phenomenon. Taking into account both the Vicsek short range ordering and also the far field hydrodynamic (HD) interactions mediated by the ambient fluid, we investigate the role of HD interaction in the ordering phenomena in an active suspension. We observe that depending on the number density of swimmers and the strength of noise, the HD interaction can either enhance or weaken the ordering in a suspension. For a fixed value of noise, at large densities of particles, long range interactions enhance the order and clustering in the system but, at smaller densities, HD decreases the order.

  6. Particle Suspension Mechanisms - Supplemental Material

    Energy Technology Data Exchange (ETDEWEB)

    Dillon, M B

    2011-03-03

    This supplemental material provides a brief introduction to particle suspension mechanisms that cause exfoliated skin cells to become and remain airborne. The material presented here provides additional context to the primary manuscript and serves as background for designing possible future studies to assess the impact of skin cells as a source of infectious aerosols. This introduction is not intended to be comprehensive and interested readers are encouraged to consult the references cited.

  7. Robust Tensioned Kevlar Suspension Design

    Science.gov (United States)

    Young, Joseph B.; Naylor, Bret J.; Holmes, Warren A.

    2012-01-01

    One common but challenging problem in cryogenic engineering is to produce a mount that has excellent thermal isolation but is also rigid. Such mounts can be achieved by suspending the load from a network of fibers or strings held in tension. Kevlar fibers are often used for this purpose owing to their high strength and low thermal conductivity. A suite of compact design elements has been developed to improve the reliability of suspension systems made of Kevlar.

  8. Control of mechatronic systems using electrorheological fluids; ER ryutai wo mochiita mekatoronikusu kiki no seigyo

    Energy Technology Data Exchange (ETDEWEB)

    Furusho, J. [The Univ. of Electric Communications, Tokyo (Japan)

    1995-09-10

    ER fluids (electrorheological fluids) are fluids whose rheological properties vary due to an electric field, and at the present, its development is being vigorously carried forward with the objective of its application to various mechanical systems. The ER fluids which are the objects for its development are two kinds, namely ER suspensions and homogeneous fluids using liquid crystals. Concerning the ER suspensions, its study started from the latter half of 1940`s, but the history of studying the homogeneous ER fluids is short. In this article, comparison is made between the ER suspensions and the homogeneous ER fluids. Regarding the comparison in their application fields, several differences are enumerated including that the response time of the ER suspensions to the change of the electric field is considerably faster than the homogeneous fluids using liquid crystals. As examples of the application of the ER suspensions, ER valves, application to automobiles, ER dampers, vibration control of structures, and ER clutches are shown and likewise, as examples of the application of the homogeneous ER fluids, robot arm control, dampers, etc.. Also its application to robotics is described. 51 refs., 8 figs., 1 tab.

  9. Viscosity of aqueous and cyanate ester suspensions containing alumina nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Lawler, Katherine [Iowa State Univ., Ames, IA (United States)

    2009-01-01

    be the cause of the viscosity reduction. The flow behavior of alumina particles in water and BECy is markedly different. Aqueous alumina suspensions are shear thinning at all alumina loadings and capable of 50 vol% loading before losing fluidity whereas BECy/alumina suspensions show Newtonian behavior up to 5 vol%, and above 5 vol% show shear thinning at all shear rates. Highly loaded suspensions (i.e. 20vol% alumina) exhibit shear thinning at low and moderate shear rates and shear thickening at higher shear rates. The maximum particle loading for a fluid suspension, in this case, appears to be about 20 vol%. The difference in the viscosity of these suspensions must be related to the solvent-particle interactions for each system. The reason is not exactly known, but there are some notable differences between BECy and water. Water molecules are {approx}0.28 nm in length and highly hydrogen bonded with a low viscosity (1 mPa's) whereas in the cyanate ester (BECy) system, the solvent molecule is about 1.2 nm, in the largest dimension, with surfaces of varied charge distribution throughout the molecule. The viscosity of the monomer is also reasonably low for organic polymer precursor, about 7 mPa's. Nanoparticles in water tend to agglomerate and form flocs which are broken with the shear force applied during viscosity measurement. The particle-particle interaction is very important in this system. In BECy, the particles appear to be well dispersed and not as interactive. The solvent-particle interaction appears to be most important. It is not known exactly how the alumina particles interact with the monomer, but NMR suggests hydrogen bonding. These hydrogen bonds between the particle and monomer could very well affect the viscosity. A conclusion that can be reached in this work is that the presence of hydroxyl groups on the surface of the alumina particles is significant and seems to affect the interactions between other particles and the solvent. Thus, the

  10. Viscosity of aqueous and cyanate ester suspensions containing alumina nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Lawler, Katherine [Iowa State Univ., Ames, IA (United States)

    2009-01-01

    be the cause of the viscosity reduction. The flow behavior of alumina particles in water and BECy is markedly different. Aqueous alumina suspensions are shear thinning at all alumina loadings and capable of 50 vol% loading before losing fluidity whereas BECy/alumina suspensions show Newtonian behavior up to 5 vol%, and above 5 vol% show shear thinning at all shear rates. Highly loaded suspensions (i.e. 20vol% alumina) exhibit shear thinning at low and moderate shear rates and shear thickening at higher shear rates. The maximum particle loading for a fluid suspension, in this case, appears to be about 20 vol%. The difference in the viscosity of these suspensions must be related to the solvent-particle interactions for each system. The reason is not exactly known, but there are some notable differences between BECy and water. Water molecules are {approx}0.28 nm in length and highly hydrogen bonded with a low viscosity (1 mPa's) whereas in the cyanate ester (BECy) system, the solvent molecule is about 1.2 nm, in the largest dimension, with surfaces of varied charge distribution throughout the molecule. The viscosity of the monomer is also reasonably low for organic polymer precursor, about 7 mPa's. Nanoparticles in water tend to agglomerate and form flocs which are broken with the shear force applied during viscosity measurement. The particle-particle interaction is very important in this system. In BECy, the particles appear to be well dispersed and not as interactive. The solvent-particle interaction appears to be most important. It is not known exactly how the alumina particles interact with the monomer, but NMR suggests hydrogen bonding. These hydrogen bonds between the particle and monomer could very well affect the viscosity. A conclusion that can be reached in this work is that the presence of hydroxyl groups on the surface of the alumina particles is significant and seems to affect the interactions between other particles and the solvent. Thus, the

  11. Internal waves interacting with particles in suspension

    Science.gov (United States)

    Micard, Diane

    2016-04-01

    Internal waves are produced as a consequence of the dynamic balance between buoy- ancy and gravity forces when a particle of fluid is vertically displaced in a stable stratified environment. Geophysical systems such as ocean and atmosphere are naturally stratified and therefore suitable for internal waves to propagate. Furthermore, these two environ- ments stock a vast amount of particles in suspension, which present a large spectrum of physical properties (size, density, shape), and can be organic, mineral or pollutant agents. Therefore, it is reasonable to expect that internal waves will have an active effect over the dynamics of these particles. In order to study the interaction of internal waves and suspended particles, an ide- alized experimental setup has been implemented. A linear stratification is produced in a 80×40×17 cm3 tank, in which two dimensional plane waves are created thanks to the inno- vative wave generator GOAL. In addition, a particle injector has been developed to produce a vertical column of particles within the fluid, displaying the same two-dimensional sym- metry as the waves. The particle injector allows to control the volumic fraction of particles and the size of the column. The presence of internal waves passing through the column of particles allowed to observe two main effects: The column oscillates around an equilibrium position (which is observed in both, the contours an the interior of the column), and the column is displaced as a whole. The column is displaced depending on the characteristics of the column, the gradient of the density, and the intensity and frequency of the wave. When displaced, the particles within the column are sucked towards the source of waves. The direction of the displacement of the column is explained by computing the effect of the Lagrangian drift generated by the wave over the time the particles stay in the wave beam before settling.

  12. Shear-induced fragmentation of laponite suspensions

    Science.gov (United States)

    Gibaud, Thomas; Barentin, Catherine; Taberlet, Nicolas; Manneville, Sébastien

    Simultaneous rheological and velocity profile measurements are performed in a smooth Couette geometry on Laponite suspensions seeded with glass microspheres and undergoing the shear-induced solid-to-fluid (or yielding) transition. Under these slippery boundary conditions, a rich temporal behaviour is uncovered, in which shear localization is observed at short times, that rapidly gives way to a highly heterogeneous flow characterized by intermittent switching from plug-like flow to linear velocity profiles. Such a temporal behaviour is linked to the fragmentation of the initially solid sample into blocks separated by fluidized regions. These solid pieces get progressively eroded over time scales ranging from a few minutes to several hours depending on the applied shear rate $\\dot{\\gamma}$. The steady-state is characterized by a homogeneous flow with almost negligible wall slip. The characteristic time scale for erosion is shown to diverge below some critical shear rate $\\dot{\\gamma}^\\star$ and to scale as $(\\dot{\\gamma}-\\dot{\\gamma}^\\star)^{-n}$ with $n\\simeq 2$ above $\\dot{\\gamma}^\\star$. A tentative model for erosion is discussed together with open questions raised by the present results.

  13. Fluid mechanics

    CERN Document Server

    Kundu, Pijush K; Dowling, David R

    2011-01-01

    Fluid mechanics, the study of how fluids behave and interact under various forces and in various applied situations-whether in the liquid or gaseous state or both-is introduced and comprehensively covered in this widely adopted text. Revised and updated by Dr. David Dowling, Fluid Mechanics, 5e is suitable for both a first or second course in fluid mechanics at the graduate or advanced undergraduate level. Along with more than 100 new figures, the text has been reorganized and consolidated to provide a better flow and more cohesion of topics.Changes made to the

  14. Shear thickening behavior of nanoparticle suspensions with carbon nanofillers

    Energy Technology Data Exchange (ETDEWEB)

    Sha, Xiaofei; Yu, Kejing, E-mail: yukejing@gmail.com; Cao, Haijian; Qian, Kun [Ministry of Education, Jiangnan University, Key Laboratory of Eco-textiles (China)

    2013-07-15

    Suspensions comprised of silica nanoparticle (average diameter: 650 nm) and carbon nanofillers dispersed in polyethylene glycol were prepared and investigated. Rheological measurement demonstrated that the mixed suspensions showed a non-Newtonian flow profile, and the shear thickening effect was enhanced by the addition of carbon nanotubes (CNTs) (main range of diameter: 10-20 nm; length: 5-15 {mu}m; purity: >97 wt%) and graphene nanoplatelets (GNs) (average diameter: >50 nm; average length: 20 {mu}m; purity: >92 wt%). It suggested that better the aggregation effect of dispersed particles was, the more significant the shear thickening effect achieved. The results also revealed that the formation of large nanomaterials clusters could be suitable to explain the phenomena. Furthermore, the trend of shear thickening behavior of the silica suspension with CNTs was more striking than that of GNs. The physical reactions between those multi-dispersed phases had been described by the schematic illustrations in papers. Otherwise, a model was built to explain these behaviors, which could be attributed to the unique structures and inherent properties of these two different nanofillers. And the morphologies of the shear thickening fluid which were examined by transmission electron microscopy confirmed this mechanism.

  15. Contact angle hysteresis of microbead suspensions.

    Science.gov (United States)

    Waghmare, Prashant R; Mitra, Sushanta K

    2010-11-16

    Microbead suspensions are often used in microfluidic devices for transporting biomolecules. An experimental investigation on the wettability of microbead suspension is presented in this study. The variation in the surface tension and the equilibrium contact angle with the change in the volume fraction of the microbead is presented here. The surface tension of the microbead suspension is measured with the pendant drop technique, whereas the dynamic contact angle measurements, i.e., advancing and receding contact angles, are measured with the sessile drop technique. An equilibrium contact angle of a suspension with particular volume fraction is determined by computing an average over the measured advancing and receding contact angles. It is observed that the surface tension and the equilibrium contact angle determined from advancing and receding contact angles vary with the magnitude of the microbeads volume fraction in the suspension. A decrease in the surface tension with an increase in the volume fraction of the microbead suspension is observed. The advancement and the recession in contact line for dynamic contact angle measurements are achieved with the motorized dosing mechanism. For microbead suspensions, the advancement of the contact line is faster as compared to the recession of the contact line for the same flow rate. The presence of microbeads assists in the advancement and the recession of the contact line of the suspension. A decrease in the equilibrium contact angles with an increase in the microbead suspension volume fraction is observed. Inclusion of microbeads in the suspension increases the wetting capability for the considered combination of the microbead suspension and substrate. Finally, empirical correlations for the surface tension and the contact angle of the suspension as a function of microbead volume fraction are proposed. Such correlations can readily be used to develop mechanistic models for the capillary transport of microbead

  16. EXPERIMENTAL STUDY ON VELOCITY PROFILE OF SUBMERGED ABRASIVE SUSPENSION JET FLOW

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    Abrasive jet cutting, as a more efficient machining or cutting method, has emerged in recent years in mining and machining industries, but the knowledge about velocity profile of abrasive jet flow lacks in general. In practice, the Polyacrylamide (PAM) is generally applied to jet fluid to increase the suspension of the abrasive particles. Also, the effects of PAM on jet flow are not very clear. In this paper, velocity fields of both the abrasive particles and the fluid were systematically studied with the PIV technology. The slip velocity between the abrasive particle and the surrounding fluid was subtracted out to give a further description of abrasive suspension jet. The effects of polymer PAM on both the fluid flow and the movement of the suspending abrasive particles were also measured. And it is found that the PAM is a proper type of additive to improve velocity fields for both the abrasive particles and the fluid in a jet. The results of the PIV measurement can help give a better understanding about the basic physics of abrasive suspension jet flow, and a good guidance to validate and develop reliable computational models to describe the jet.

  17. Mechanism of Off—Bottom Suspension of Solid Particles in a Mechanical Stirred Tank

    Institute of Scientific and Technical Information of China (English)

    BAOYuyun; HUANGXiongbin; 等

    2002-01-01

    The minimum fluid velocity to maintain particles just suspended was deduced,and the theoretical analysis shows that the minimum velocity is influenced by the properties of the solid and liquid,not by the operational conditions. For justification,the local minimum velocity at the bottom of the tank was measured by a bi-electrode conductivity probe,in a square-sectioned stirred tank (0.75m×0.75m×1.0m) with the glass beads-water system. The experiments showed that the fluid velocities for the same suspension state were identical despite that the power dissipated per unit mass was not the same under different configuration and operation.Both theoretical analysis and experimental results indicate that the off-bottom suspension is controlled by the local fluid flow over the bottom of the stirred tank.

  18. A modelling and experimental study of the bubble trajectory in a non-Newtonian crystal suspension

    Energy Technology Data Exchange (ETDEWEB)

    Hassan, N M S [Process Engineering and Light Metals (PELM) Centre, Faculty of Sciences, Engineering and Health, CQUniversity, Rockhampton, QLD 4702 (Australia); Khan, M M K; Rasul, M G, E-mail: m.rasul@cqu.edu.a [School of Engineering and Built Environment, Faculty of Sciences, Engineering and Health, CQUniversity, Rockhampton, QLD 4702 (Australia)

    2010-12-15

    This paper presents an experimental and computational study of air bubbles rising in a massecuite-equivalent non-Newtonian crystal suspension. The bubble trajectory inside the stagnant liquid of a 0.05% xanthan gum crystal suspension was investigated and modelled using the computational fluid dynamics (CFD) model to gain an insight into the bubble flow characteristics. The CFD code FLUENT was used for numerical simulation, and the bubble trajectory calculations were performed through a volume of fluid (VOF) model. The influences of the Reynolds number (Re), the Weber number (We) and the bubble aspect ratio (E) on the bubble trajectory are discussed. The conditions for the bubbles' path oscillations are identified. The experimental results showed that the path instability for the crystal suspension was less rapid than in water. The trajectory analysis indicated that 5.76 mm diameter bubbles followed a zigzag motion in the crystal suspension. Conversely, the smaller bubbles (5.76 mm) followed a path of least horizontal movement and larger bubbles (21.21 mm) produced more spiral motion within the crystal suspension. Path instability occurred for bubbles of 15.63 and 21.21 mm diameter, and they induced both zigzag and spiral trajectories within the crystal suspension. At low Re and We, smaller bubbles (5.76 mm) produced a zigzag trajectory, whereas larger bubbles (15.63 and 21.21 mm) showed both zigzag and spiral trajectories at intermediate and moderately high Re and We in the crystal suspension. The simulation results illustrated that a repeating pattern of swirling vortices was created for smaller bubbles due to the unstable wake and unsteady flow of these bubbles. This is the cause of the smaller bubbles moving in a zigzag way. Larger bubbles showed two counter-rotating trailing vortices at the back of the bubble. These vortices induced a velocity component to the gas-liquid interface and caused a deformation. Hence, the larger bubbles produced a path

  19. Drop Impact of Viscous Suspensions on Solid Surfaces

    Science.gov (United States)

    Bolleddula, Daniel; Aliseda, Alberto

    2009-11-01

    Droplet impact is a well studied subject with over a century of progress. Most studies are motivated by applications such as inkjet printing, agriculture spraying, or printed circuit boards. Pharmaceutically relevant fluids provide an experimental set that has received little attention. Medicinal tablets are coated by the impaction of micron sized droplets of aqueous suspensions and subsequently dried for various purposes such as brand recognition, mask unpleasant taste, or functionality. We will present a systematic study of micron sized drop impact of Newtonian and Non-Newtonian fluids used in pharmaceutical coating processes. In our experiments we extend the range of Ohnesorge numbers, O(1), of previous studies on surfaces of varying wettability and roughness.

  20. Fluid Dynamics

    DEFF Research Database (Denmark)

    Brorsen, Michael

    These lecture notes are intended mainly for the 7th semester course "Fluid Dynamics" offered by the Study Committee on Civil Engineering, Aalborg University.......These lecture notes are intended mainly for the 7th semester course "Fluid Dynamics" offered by the Study Committee on Civil Engineering, Aalborg University....

  1. PERCOLATION TRANSITION IN ELECTRORHEOLOGICAL FLUIDS

    Institute of Scientific and Technical Information of China (English)

    HAO Tian; CHEN Yihong; XU Zhengmiao; XU Yuanze; HUANG Yun

    1994-01-01

    The electric conductivity, dynamic modulus and yield stress of the developed electrorheological fluid (ERF) are measured at different volume fraction and different electric field strength using a modified Rheosetrics Mechanical Spectrometer (Model 605). The percolation theory is introduced to explain electrorheological effect and found that the ERF's have the similar percolated network structure as that of other ordinary suspensions with a critical volume fraction value independent of electric field strength. A master curve of dimensionless modulus against dimensionless volume fraction is obtained. which shows that the essence of ER phenomenon actually is one kind of the second ofder phase transition.

  2. Rheology, microstructure and migration in brownian colloidal suspensions.

    Science.gov (United States)

    Pan, Wenxiao; Caswell, Bruce; Karniadakis, George Em

    2010-01-05

    We demonstrate that suspended spherical colloidal particles can be effectively modeled as single dissipative particle dynamics (DPD) particles provided that the conservative repulsive force is appropriately chosen. The suspension model is further improved with a new formulation, which augments standard DPD with noncentral dissipative shear forces between particles while preserving angular momentum. Using the new DPD formulation we investigate the rheology, microstructure and shear-induced migration of a monodisperse suspension of colloidal particles in plane shear flows (Couette and Poiseuille). Specifically, to achieve a well-dispersed suspension we employ exponential conservative forces for the colloid-colloid and colloid-solvent interactions but keep the conventional linear force for the solvent-solvent interactions. Our simulations yield relative viscosity versus volume fraction predictions in good agreement with both experimental data and empirical correlations. We also compute the shear-dependent viscosity and the first and second normal-stress differences and coefficients in both Couette and Poiseuille flow. Simulations near the close packingvolume-fraction (64%) at low shear rates demonstrate a transition to flow-induced string-like structures of colloidal particles simultaneously with a transition to a nonlinear Couette velocity profile in agreement with experimental observations. After a sufficient increase ofthe shear rate the ordered structure melts into disorder with restoration of the linear velocity profile. Migration effects simulated in Poiseuille flow compare well with experiments and model predictions. The important role of angular momentum and torque in nondilute suspensions is also demonstrated when compared with simulations by the standard DPD, which omits the angular degrees of freedom. Overall, the new method agrees very well with the Stokesian Dynamics method but it seems to have lower computational complexity and is applicable to general

  3. Fluidization Characteristics of Medium-High-Consistency Pulp Fiber Suspensions with an Impeller

    Directory of Open Access Journals (Sweden)

    Ye Daoxing

    2016-01-01

    Full Text Available When the mass concentration exceeds 7%, pulp suspensions stop flowing and act like a solid. To investigate the fluidization characteristics of medium-high-consistency pulp suspensions and achieve pulp fluidization and pumping, experiments were carried out with waste tissue pulp and unbleached kraft pulp. The objectives of this paper were to study the rheology of medium-high-consistency pulp and to determine accurate parameters for the physical Herschel-Bulkley model. To validate this model, computational fluid dynamics (CFD results were compared to experimental data. The simulation values were very similar and were in agreement with experimental results.

  4. Shear thickening in non-Brownian suspensions: an excluded volume effect

    CERN Document Server

    Picano, Francesco; Mitra, Dhrubaditya; Brandt, Luca

    2013-01-01

    Shear-thickening appears as an increase of the viscosity of a dense suspension with the shear rate, sometimes sudden and violent at high volume fraction. Its origin for non-colloidal suspension with non negligible inertial effects is still debated. Here we consider a simple shear flow and demonstrate that fluid inertia causes a strong microstructure anisotropy that results in the formation of a wake region with no relative flux of particles. We show that shear-thickening at finite inertia can be explained as an increase of the effective volume fraction when considering the dynamically excluded volume due to these wake regions.

  5. Drag Reduction of Bacterial Cellulose Suspensions

    Directory of Open Access Journals (Sweden)

    Satoshi Ogata

    2011-01-01

    Full Text Available Drag reduction due to bacterial cellulose suspensions with small environmental loading was investigated. Experiments were carried out by measuring the pressure drop in pipe flow. It was found that bacterial cellulose suspensions give rise to drag reduction in the turbulent flow range. We observed a maximum drag reduction ratio of 11% and found that it increased with the concentration of the bacterial cellulose suspension. However, the drag reduction effect decreased in the presence of mechanical shear.

  6. Modeling and analysis of electrorheological suspensions in shear flow.

    Science.gov (United States)

    Seo, Youngwook P; Seo, Yongsok

    2012-02-14

    A model capable of describing the flow behavior of electrorheological (ER) suspensions under different electric field strengths and over the full range of shear rates is proposed. Structural reformation in the low shear rate region is investigated where parts of a material are in an undeformed state, while aligned structures reform under the shear force. The model's predictions were compared with the experimental data of some ER fluids as well as the CCJ (Cho-Choi-Jhon) model. This simple model's predictions of suspension flow behavior with subsequent aligned structure reformation agreed well with the experimental data, both quantitatively and qualitatively. The proposed model plausibly predicted the static yield stress, whereas the CCJ model and the Bingham model predicted only the dynamic yield stress. The master curve describing the apparent viscosity was obtained by appropriate scaling both axes, which showed that a combination of dimensional analysis and flow curve analysis using the proposed model yielded a quantitatively and qualitatively precise description of ER fluid rheological behavior based on relatively few experimental measurements.

  7. Time Varying Behavior of the Loudspeaker Suspension

    DEFF Research Database (Denmark)

    Pedersen, Bo Rohde; Agerkvist, Finn T.

    2007-01-01

    The suspension part of the electrodynamic loudspeaker is often modelled as a simple linear spring with viscous damping, however the dynamic behaviour of the suspension is much more complicated than predicted by such a simple model. At higher levels the compliance becomes non-linear and often...... changes during excitation at high levels. This paper investigates how the compliance of the suspension depends on the excitation, i.e. level and frequency content. The measurements are compared with other known measurement methods of the suspension....

  8. Fluid dynamics of dilatant fluid

    DEFF Research Database (Denmark)

    Nakanishi, Hiizu; Nagahiro, Shin-ichiro; Mitarai, Namiko

    2012-01-01

    A dense mixture of granules and liquid often shows a severe shear thickening and is called a dilatant fluid. We construct a fluid dynamics model for the dilatant fluid by introducing a phenomenological state variable for a local state of dispersed particles. With simple assumptions for an equation...... of the state variable, we demonstrate that the model can describe basic features of the dilatant fluid such as the stress-shear rate curve that represents discontinuous severe shear thickening, hysteresis upon changing shear rate, and instantaneous hardening upon external impact. An analysis of the model...... reveals that the shear thickening fluid shows an instability in a shear flow for some regime and exhibits the shear thickening oscillation (i.e., the oscillatory shear flow alternating between the thickened and the relaxed states). The results of numerical simulations are presented for one- and two...

  9. Fluid dynamics

    CERN Document Server

    Bernard, Peter S

    2015-01-01

    This book presents a focused, readable account of the principal physical and mathematical ideas at the heart of fluid dynamics. Graduate students in engineering, applied math, and physics who are taking their first graduate course in fluids will find this book invaluable in providing the background in physics and mathematics necessary to pursue advanced study. The book includes a detailed derivation of the Navier-Stokes and energy equations, followed by many examples of their use in studying the dynamics of fluid flows. Modern tensor analysis is used to simplify the mathematical derivations, thus allowing a clearer view of the physics. Peter Bernard also covers the motivation behind many fundamental concepts such as Bernoulli's equation and the stream function. Many exercises are designed with a view toward using MATLAB or its equivalent to simplify and extend the analysis of fluid motion including developing flow simulations based on techniques described in the book.

  10. 基于混合模式的汽车磁流变减振器阻尼特性分析与测试%ANALYSIS AND TESTING OF A MAGNETORHEOLOGICAL FLUID SHOCK ABSORBER BASED ON MIXED MODE FOR AUTOMOBILE SUSPENSION SYSTEMS

    Institute of Scientific and Technical Information of China (English)

    廖昌荣; 陈伟民; 余淼; 黄尚廉

    2001-01-01

    A magnetorheological fluid (MR fluid)shock absorber model is analyzed theoretically using Newtonain fluid and idealized nonlinear Bingham plastic model respectively for the mixed mode of flow mode and shear mode. In the light of the technician requirements for Changan mini-automobile, a MR fluid shock absorber is designed and fabricated using commercial MR fluid. The nonlinear MR fluid shock absorber model is validated experimentally. The results reveal that the shock absorber model is reasonable and the MR fluid shock absorber for a specific application can be designed according to the MR fluid shock absorber model presented.%根据牛顿流体模型和滨汉塑性流体模型,分别对混合工作模式的汽车磁流变减振器进行了理论分析研究。按照长安微型汽车的技术要求,设计和制作了汽车磁流变减振器,并对此进行了试验测试。试验结果表明,应用所提出的理论分析模型是可行的,对设计特殊阻尼特性的磁流变减振器有一定的指导意义。

  11. Coupling between bulk- and surface chemistry in suspensions of charged colloids

    Science.gov (United States)

    Heinen, M.; Palberg, T.; Löwen, H.

    2014-03-01

    The ionic composition and pair correlations in fluid phases of realistically salt-free charged colloidal sphere suspensions are calculated in the primitive model. We obtain the number densities of all ionic species in suspension, including low-molecular weight microions, and colloidal macroions with acidic surface groups, from a self-consistent solution of a coupled physicochemical set of nonlinear algebraic equations and non-mean-field liquid integral equations. Here, we study suspensions of colloidal spheres with sulfonate or silanol surface groups, suspended in demineralized water that is saturated with carbon dioxide under standard atmosphere. The only input required for our theoretical scheme are the acidic dissociation constants pKa, and effective sphere diameters of all involved ions. Our method allows for an ab initio calculation of colloidal bare and effective charges, at high numerical efficiency.

  12. Electrorheological Damper and Its Application for Semi-Active Suspension System

    Institute of Scientific and Technical Information of China (English)

    ZHAO Xia; ZHANG Yong-fa

    2007-01-01

    A semi-active control of vehicle suspension system with electrorheological (ER) damper is presented.ER fluid characteristics are introduced based on the Bingham plasticity model first.Then ER damper working force is given.Finally a quarter car model with ER damper is constructed.The skyhook control strategy is adopted to simulate the amplitude-frequency characteristics and the vibration of suspension system under random road excitation on the basis of ER damper characteristics.The response curves of the vertical acceleration,the suspension dynamic working space and the tyre dynamic loading are obtained.Simulation results show that the acceleration is reduced effectively and then the ride comfort is improved by the skyhook control law.

  13. Suspension restraint - Induced hypokinesia and antiorthostasis as a simulation of weightlessness

    Science.gov (United States)

    Musacchia, X. J.; Steffen, J. M.; Deavers, D. R.

    1982-01-01

    Muscle, renal, fluid and electrolyte responses were measured in suspended rats; the hind limbs are non-load bearing and the front limbs can be used for feeding and grooming. Hind limb hypokinesia reverses after removal from the suspension harness. This suspension system is adjustable for a head-down tilt to produce antiorthostatic responses which are also reversible. Responses to hypokinesia or antiorthostatic hypokinesia for up to 14 days were measured, e.g., muscle atrophy: soleus greater than gastrocnemius equals plantaris greater than extensor digitorum longus, kaliuresis, and increased excretion of urea, NH3, and 3 methylhistidine. Muscle protein loss, a response to a reduction in RNA, is also reversible. A head-down tilt for 7-14 days results in diuresis and natriuresis. These changes are reversed within 24 hours after removal from the restraint harness. Physiological effects of suspension restraint can be used to simulate and predict responses to microgravity exposure.

  14. Imaging the Microscopic Structure of Shear Thinning and Thickening Colloidal Suspensions

    KAUST Repository

    Cheng, X.

    2011-09-01

    The viscosity of colloidal suspensions varies with shear rate, an important effect encountered in many natural and industrial processes. Although this non-Newtonian behavior is believed to arise from the arrangement of suspended particles and their mutual interactions, microscopic particle dynamics are difficult to measure. By combining fast confocal microscopy with simultaneous force measurements, we systematically investigate a suspension\\'s structure as it transitions through regimes of different flow signatures. Our measurements of the microscopic single-particle dynamics show that shear thinning results from the decreased relative contribution of entropic forces and that shear thickening arises from particle clustering induced by hydrodynamic lubrication forces. This combination of techniques illustrates an approach that complements current methods for determining the microscopic origins of non-Newtonian flow behavior in complex fluids.

  15. Computer Simulation Study of Collective Phenomena in Dense Suspensions of Red Blood Cells under Shear

    CERN Document Server

    Krüger, Timm

    2012-01-01

    The rheology of dense red blood cell suspensions is investigated via computer simulations based on the lattice Boltzmann, the immersed boundary, and the finite element methods. The red blood cells are treated as extended and deformable particles immersed in the ambient fluid. In the first part of the work, the numerical model and strategies for stress evaluation are discussed. In the second part, the behavior of the suspensions in simple shear flow is studied for different volume fractions, particle deformabilities, and shear rates. Shear thinning behavior is recovered. The existence of a shear-induced transition from a tumbling to a tank-treading motion is demonstrated. The transition can be parameterized by a single quantity, namely the effective capillary number. It is the ratio of the suspension stress and the characteristic particle membrane stress. At the transition point, a strong increase in the orientational order of the red blood cells and a significant decrease of the particle diffusivity are obser...

  16. 39 CFR 955.28 - Suspension.

    Science.gov (United States)

    2010-07-01

    ... 39 Postal Service 1 2010-07-01 2010-07-01 false Suspension. 955.28 Section 955.28 Postal Service UNITED STATES POSTAL SERVICE PROCEDURES RULES OF PRACTICE BEFORE THE POSTAL SERVICE BOARD OF CONTRACT APPEALS § 955.28 Suspension. (a) Whenever at any time it appears that the parties are in agreement as to...

  17. Time Variance of the Suspension Nonlinearity

    DEFF Research Database (Denmark)

    Agerkvist, Finn T.; Pedersen, Bo Rohde

    2008-01-01

    . This paper investigates the changes in compliance the driving signal can cause, this includes low level short duration measurements of the resonance frequency as well as high power long duration measurements of the non-linearity of the suspension. It is found that at low levels the suspension softens...

  18. Active suspension for a field sprayer boom

    DEFF Research Database (Denmark)

    Nielsen, Henrik Skovsgaard; Sørensen, Paul Haase

    1998-01-01

    The possibilities of implementing an active boom suspension is investigated. The performance improvement of an active suspension over a traditional passive one is studied in simulation, and shows a significant improvement. A closed-loop control system involving two ultrasonic distance transducers...

  19. 34 CFR 85.1015 - Suspension.

    Science.gov (United States)

    2010-07-01

    ... 34 Education 1 2010-07-01 2010-07-01 false Suspension. 85.1015 Section 85.1015 Education Office of the Secretary, Department of Education GOVERNMENTWIDE DEBARMENT AND SUSPENSION (NONPROCUREMENT..., pending completion of an agency investigation and any judicial or administrative proceedings that may...

  20. 36 CFR 25.3 - Supervision; suspensions.

    Science.gov (United States)

    2010-07-01

    ... 36 Parks, Forests, and Public Property 1 2010-07-01 2010-07-01 false Supervision; suspensions. 25.3 Section 25.3 Parks, Forests, and Public Property NATIONAL PARK SERVICE, DEPARTMENT OF THE INTERIOR NATIONAL MILITARY PARKS; LICENSED GUIDE SERVICE REGULATIONS § 25.3 Supervision; suspensions. (a) The...

  1. Ultrasonic characterization of shear thickening suspensions

    Science.gov (United States)

    Johnson, Benjamin Lenihan

    This dissertation describes the characterization of an inherently inhomogeneous medium capable of shear thickening. An aqueous suspension of cornstarch represents an important exemplar of such physical systems. The physics underlying the behavior of such shear thickening suspensions is incompletely understood. Characterization of these suspensions may provide valuable clues into the underlying mechanisms that result in shear thickening behavior. The goal of this thesis is to characterize the acoustic properties of suspensions of cornstarch in density-matched cesium chloride aqueous solutions. A review of the literature indicated that almost no information concerning the ultrasonic characteristics of suspensions of starches had been reported other than studies monitoring the gelatinization of starches not relevant to the shear stiffening of ungelatinized suspensions. Each chapter began with a discussion and validation of the specific experimental techniques and methods of analysis necessary for each type of measurement. Ultrasonic measurement of the group velocity, the frequency-dependent attenuation properties, the frequency-dependent phase velocity, and the frequency-dependent backscatter properties of the suspensions of cornstarch are reported. Initially counterintuitive results including negative (phase velocity) dispersion and a decrease in the measured backscatter coefficient with increasing particle concentration are understood in terms of widely accepted physical models. In sum, these studies represent an advancement of the understanding of the physics underlying the interaction between ultrasound and suspensions and lay the groundwork for future studies probing the physics of the shear thickening.

  2. Alternatives to Suspension: A Government Initiative

    Science.gov (United States)

    Ryan, Thomas G.; Zoldy, Scott

    2011-01-01

    Student discipline and the ineffectiveness of out-of-school suspension is examined in light of the Ontario (Canada) legislative reform that supported a greater emphasis on progressive discipline alternatives to out-of-school suspension. Alternative discipline herein is explored via the behavior education plan, the school survival group, and…

  3. 25 CFR 242.7 - Suspension.

    Science.gov (United States)

    2010-04-01

    ... 25 Indians 1 2010-04-01 2010-04-01 false Suspension. 242.7 Section 242.7 Indians BUREAU OF INDIAN AFFAIRS, DEPARTMENT OF THE INTERIOR FISH AND WILDLIFE COMMERCIAL FISHING ON RED LAKE INDIAN RESERVATION § 242.7 Suspension. All commercial fishing operations may be suspended by order of the Secretary at...

  4. 32 CFR 552.77 - Suspension approval.

    Science.gov (United States)

    2010-07-01

    ... 32 National Defense 3 2010-07-01 2010-07-01 true Suspension approval. 552.77 Section 552.77 National Defense Department of Defense (Continued) DEPARTMENT OF THE ARMY MILITARY RESERVATIONS AND....77 Suspension approval. The installation commander will personally approve all cases in...

  5. 21 CFR 520.1289 - Lufenuron suspension.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 6 2010-04-01 2010-04-01 false Lufenuron suspension. 520.1289 Section 520.1289 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) ANIMAL DRUGS, FEEDS, AND RELATED PRODUCTS ORAL DOSAGE FORM NEW ANIMAL DRUGS § 520.1289 Lufenuron suspension....

  6. 49 CFR 238.227 - Suspension system.

    Science.gov (United States)

    2010-10-01

    ... 49 Transportation 4 2010-10-01 2010-10-01 false Suspension system. 238.227 Section 238.227 Transportation Other Regulations Relating to Transportation (Continued) FEDERAL RAILROAD ADMINISTRATION... Equipment § 238.227 Suspension system. On or after November 8, 1999— (a) All passenger equipment...

  7. 32 CFR 1609.5 - Suspension.

    Science.gov (United States)

    2010-07-01

    ... 32 National Defense 6 2010-07-01 2010-07-01 false Suspension. 1609.5 Section 1609.5 National Defense Other Regulations Relating to National Defense SELECTIVE SERVICE SYSTEM UNCOMPENSATED PERSONNEL § 1609.5 Suspension. The Director of Selective Service may suspend from duty any uncompensated...

  8. Some specific features of the NMR study of fluid flows

    Science.gov (United States)

    Davydov, V. V.

    2016-07-01

    Some specific features of studying fluid flows with a NMR spectrometer are considered. The consideration of these features in the NMR spectrometer design makes it possible to determine the relative concentrations of paramagnetic ions and measure the longitudinal and transverse relaxation times ( T 1 and T 2, respectively) in fluid flows with an error no larger than 0.5%. This approach allows one to completely avoid errors in determining the state of a fluid from measured relaxation constants T 1 and T 2, which is especially urgent when working with medical suspensions and biological solutions. The results of an experimental study of fluid flows are presented.

  9. Collective Chemotactic Dynamics in the Presence of Self-Generated Fluid Flows

    CERN Document Server

    Lushi, Enkeleida; Shelley, Michael J

    2012-01-01

    In micro-swimmer suspensions locomotion necessarily generates fluid motion, and it is known that such flows can lead to collective behavior from unbiased swimming. We examine the complementary problem of how chemotaxis is affected by self-generated flows. A kinetic theory coupling run-and-tumble chemotaxis to the flows of collective swimming shows separate branches of chemotactic and hydrodynamic instabilities for isotropic suspensions, the first driving aggregation, the second producing increased orientational order in suspensions of "pushers" and maximal disorder in suspensions of "pullers". Nonlinear simulations show that hydrodynamic interactions can limit and modify chemotactically-driven aggregation dynamics. In puller suspensions the dynamics form aggregates that are mutually-repelling due to the non-trivial flows. In pusher suspensions chemotactic aggregation can lead to destabilizing flows that fragment the regions of aggregation.

  10. Automobile active suspension system with fuzzy control

    Institute of Scientific and Technical Information of China (English)

    刘少军; 黄中华; 陈毅章

    2004-01-01

    A quarter-automobile active suspension model was proposed. High speed on/off solenoid valves were used as control valves and fuzzy control was chosen as control method . Based on force analyses of system parts, a mathematical model of the active suspension system was established and simplified by linearization method. Simulation study was conducted with Matlab and three scale coefficients of fuzzy controller (ke, kec, ku) were acquired. And an experimental device was designed and produced. The results indicate that the active suspension system can achieve better vibration isolation performance than passive suspension system, the displacement amplitude of automobile body can be reduced to 55%. Fuzzy control is an effective control method for active suspension system.

  11. Equilibrium and dynamic simulations of bidisperse suspensions

    Science.gov (United States)

    Jacobson, Charles Andrew

    Monte Carlo simulations are being used to investigate the structural behavior of bidisperse colloidal (silica) liquids. The solids volume fraction is 40%, and the bidispersity is characterized by two parameters: alpha, the particle size ratio, and beta, the relative volume fraction of small particles over the total volume fraction of solids. Four different size ratios are used (two, three, four, and five-to-one). The largest particle size is 0.6 mum, while the smallest is 0.12 mum. The variables (electrolyte concentration, surface potential, etc.) of the potential are set to ensure the system is stable and non-flocculating. The radial distribution function g(r) for all combinations (small-small, small-large, and large-large) of particles along with the osmotic compressibility is calculated for the various size ratios at different beta values. There are two interesting changes between the monodisperse and bidisperse suspensions. First, g(r) for the large-large particles shows an interesting structural change in that the HCP (hexagonal close packing) structure for the monodisperse large particles evolves to a BCC-like (body centered cubic) structure as beta is increased. There is also an indication of phase separation which may be a consequence of depletion flocculation. These changes appear to occur for all size ratios that have been investigated. Also, the HCP (hexagonal close packing) structure for the monodisperse small particles is completely broken up when added to the large particle system. Second, the structural change appears approximately at the beta value corresponding to the minimum in the osmotic compressibility. The structure factor is also calculated from the Fourier transform of the radial distribution function. It is suggested as future work to obtain an effective potential between large particle potentials, treating the small particle-laden fluid as a continuum. This effective potential, which can be obtained using an inversion scheme, may indicate

  12. Suspension-Firing of Biomass

    DEFF Research Database (Denmark)

    Bashir, Muhammad Shafique; Jensen, Peter Arendt; Frandsen, Flemming;

    2012-01-01

    , followed the same trends. Ash transformation was investigated by bulk ash analysis of the fuel, fly, and bottom ash during straw and/or wood suspension firing. Bulk ash analysis of fly ashes showed that the contents of volatile elements (K, Cl, S) were slightly greater than in the fuel ash, while Ca and Si...... in the analysis of the data. The first is the integral deposit formation rate (IDF-rate) found by dividing the integral mass change over integral time intervals (of order several hours) by the time interval. The IDF-rate is similar to deposit formation rates based on total deposit mass uptake divided by probe...... smoothing the derivatives to remove excessive noise. The DDF-rate was influenced by flue gas temperature and straw share, while changes in probe surface temperature had no significant influence. The IDF-rate, qualitatively related to the ratio between the time-integrated DDF-rate and the integration time...

  13. R fluids

    Directory of Open Access Journals (Sweden)

    Caimmi R.

    2008-01-01

    Full Text Available A theory of collisionless fluids is developed in a unified picture, where nonrotating (Ωf1 = Ωf2 = Ωf3 = 0 figures with some given random velocity component distributions, and rotating (Ωf1 = Ωf2 = Ωf3 figures with a different random velocity component distributions, make adjoint configurations to the same system. R fluids are defined as ideal, self-gravitating fluids satisfying the virial theorem assumptions, in presence of systematic rotation around each of the principal axes of inertia. To this aim, mean and rms angular velocities and mean and rms tangential velocity components are expressed, by weighting on the moment of inertia and the mass, respectively. The figure rotation is defined as the mean angular velocity, weighted on the moment of inertia, with respect to a selected axis. The generalized tensor virial equations (Caimmi and Marmo 2005 are formulated for R fluids and further attention is devoted to axisymmetric configurations where, for selected coordinate axes, a variation in figure rotation has to be counterbalanced by a variation in anisotropy excess and vice versa. A microscopical analysis of systematic and random motions is performed under a few general hypotheses, by reversing the sign of tangential or axial velocity components of an assigned fraction of particles, leaving the distribution function and other parameters unchanged (Meza 2002. The application of the reversion process to tangential velocity components is found to imply the conversion of random motion rotation kinetic energy into systematic motion rotation kinetic energy. The application of the reversion process to axial velocity components is found to imply the conversion of random motion translation kinetic energy into systematic motion translation kinetic energy, and the loss related to a change of reference frame is expressed in terms of systematic motion (imaginary rotation kinetic energy. A number of special situations are investigated in greater

  14. Effective shear viscosity and dynamics of suspensions of micro-swimmers at moderate concentrations

    Energy Technology Data Exchange (ETDEWEB)

    Constantin, Lipnikov [Los Alamos National Laboratory; Gyrya, V [PENNSYLVANIA STATE UNIV.; Aronson, I [ANL; Berlyand, L [PENNSYLVANIA STATE UNIV.

    2009-01-01

    Recently, there have been a number of experimental studies suggesting that a suspension of self-propelled bacteria (microswimmers in general) may have an effective viscosity significantly smaller than the viscosity of the ambient fluid. This is in sharp contrast with suspensions of hard passive inclusions, whose presence always increases the viscosity. Here we present a 2D model for a suspension of microswimmers in a fluid and analyze it analytically in the dilute regime (no swimmer-swimmer interactions) and numerically using a Mimetic Finite Difference discretization. Our analysis shows that in the dilute regime the effective shear viscosity is not affected by self-propulsion. But at the moderate concentrations (due to swimmer-swimmer interactions) the effective viscosity decreases linearly as a function of the propulsion strength of the swimmers. These findings prove that (i) a physically observable decrease of viscosity for a suspension of self-propelled bacteria can be explained purely by hydrodynamic interactions and (ii) self-propulsion and interaction of swimmers are both essential to the reduction of the effective shear viscosity. We performed a number of numerical experiments analyzing the dynamics of swimmers resulting from pairwise interactions. The numerical results agree with the physically observed phenomena (e.g., attraction of swimmer to swimmer and swimmer to the wall). This is viewed as an additional validation of the model and the numerical scheme.

  15. Rheological characteristics of cell suspension and cell culture of Perilla frutescens.

    Science.gov (United States)

    Zhong, J J; Seki, T; Kinoshita, S; Yoshida, T

    1992-12-01

    Physical properties such as viscosity, fluid dynamic behavior of cell suspension, and size distribution of cell aggregates of a plant, Perilla frustescens, cultured in a liquid medium were studied. As a result of investigations using cells harvester after 12 days of cultivation in a flask, it was found that the apparent viscosity of the cell suspension did not change with any variation of cell concentration below 5 g dry cell/L but markedly increased when the cell concentration increased over 12.8 g dry cell/L. The cell suspension exhibited the characteristics of a Bingham plastic fluid with a small yield stress. The size of cell aggregates in the range 74 to 500 mum did not influence the rheological characteristics of the cell suspension. The rheological characteristics of cultivation mixtures of P. frutescens cultivated in a flask and in a bioreactor were also investigated. The results showed that the flow characteristics of the cell culture could be described by a Bingham plastic model. At the later stage of cultivation, the apparent viscosity increased steadily, even though the biomass concentration (by dry weight) decreased, due to the increase of individual cell size.

  16. A seat suspension with a rotary magnetorheological damper for heavy duty vehicles

    Science.gov (United States)

    Sun, S. S.; Ning, D. H.; Yang, J.; Du, H.; Zhang, S. W.; Li, W. H.

    2016-10-01

    This paper presents the development of an innovative seat suspension working with a rotary magnetorheological (MR) fluid damper. Compared with a conventional linear MR damper, the well-designed rotary MR damper possesses several advantages such as usage reduction of magnetorheological fluid, low sealing requirements and lower costs. This research starts with the introduction of the seat suspension structure and the damper design, followed by the property test of the seat suspension using an MTS machine. The field-dependent property, amplitude-dependent performance, and the frequency-dependent performance of the new seat suspension are measured and evaluated. This research puts emphasis on the evaluation of the vibration reduction capability of the rotary MR damper by using both simulation and experimental methods. Fuzzy logic is chosen to control the rotary MR damper in real time and two different input signals are considered as vibration excitations. The experimental results show that the rotary MR damper under fuzzy logic control is effective in reducing the vibrations.

  17. Electrorheological behavior of suspensions of camphorsulfonic acid (CSA) doped polyaniline nanofibers in silicone oil

    Science.gov (United States)

    Goswami, S.; Gonçalves, P.; Cidade, M. T.

    2017-07-01

    The electrorheological (ER) effect is known as the enhancement of the apparent viscosity upon application of an external electric field applied perpendicular to the flow direction. Suspensions of polarizable particles in non-conducting solvents are the most studied ER fluids. The increase in viscosity observed in the suspensions is due to the formation of columns that align with the electric field. This work presents the ER behavior of suspensions, in silicone oil, of camphorsulfonic acid (CSA) doped polyaniline (PANI) nanofibers. The ER properties of the suspensions were investigated with a rotational rheometer, to which an ER cell was coupled, in steady shear, and electrical field strengths up to 2 kV mm-1. The effects of the electric field strength, content of nanostructures and viscosity of the continuum phase, in the shear viscosity and yield stress, were investigated at room temperature. As expected, the ER effect increases with the increase of the electric field as well as with the increase of content of nanofibers and it decreases with the increase of the oil viscosity. The suspensions present giant ER effects (higher than 2 orders of magnitude increase in viscosity for low shear rates and high electric fields), showing their potential application as ER smart materials.

  18. Research on Damping Noncoincidence and Its Influence Factors of Multibranch Hydropneumatic Suspension

    Directory of Open Access Journals (Sweden)

    Junwei Zhang

    2015-01-01

    Full Text Available Multibranch interconnected hydropneumatic suspension (MIHS is increasingly applied in heavy multiaxle vehicle (HMV for its superior characteristics, such as adjustable damping, and the antiroll and balancing axle load ability. However, as for multibranch hydropneumatic suspension, the stiffness and damping are coupled with each other tightly, which represents damping noncoincidence (DNC problem. The DNC problem has become a key obstacle for developing suspension control technology and improving suspension performance. Firstly, a kind of MIHS structure is developed for an HMV, and the interconnected structure and principle are explained. Then the DNC problem is proposed and is given a description. And then, according to the researching needs, the suspension system model of single cylinder connected with multiple branches is built up based on the knowledge of state change of fluid and gas. Fourthly, the root cause of DNC problem is given according to simulation results. Fifthly, the impacts of three factors on DNC problem are studied, respectively, by adjusting excitation signal and system parameters in the simulation. The simulation results are quantitatively compared with regard to damping noncoincidence rate (DNCR. In the end, some conclusions are drawn based on the discussion and analysis and the future work is proposed.

  19. Synthesis of silicone magnetic fluid for use in eye surgery

    Science.gov (United States)

    Dailey, J. P.; Phillips, J. P.; Li, C.; Riffle, J. S.

    1999-04-01

    Retinal detachment is repaired by external and internal tamponade. There is as yet no direct internal tamponade which provides 360° coverage to the retina. With a magnetized encircling scleral buckle, magnetic fluids would provide 360° encircling internal tamponade. Our magnetic fluid is a dispersion of ultrafine (4-10 nm) magnetic particles in silicone secured with triblock copolymer steric stabilizers. Triblock copolymers are good steric stabilizers for suspensions of γ-Fe 2O 3 powder in octamethylcyclotetrasiloxane (D 4).

  20. Premiminary tests on modified clays for electrolyte contaminated drilling fluids

    OpenAIRE

    den Hamer, Davina; Di Emidio, Gemmina; Bezuijen, Adam; Verastegui Flores, Daniel

    2015-01-01

    The quality of a bentonite suspension declines in aggressive systems like brackish or saline pore water. An engineered clay (HYPER clay) was developed for sealing materials with enhanced resistance to aggressive conditions. The modified clay is produced by treating a sodium activated bentonite with a cellulose polymer following the HYPER clay process method. This study investigates the suitability of the modified clay for electrolyte contaminated drilling fluids. Drilling fluids become contam...

  1. Practice-Relevant Aspects of Constructing ER Fluid Actuators

    Science.gov (United States)

    Janocha, H.; Rech, B.; Bölter, R.

    The flow resistance of electrorheological fluids (ER fluids) can be controlled by applying electric fields. Thus, ER fluids are suitable for the application in actuators, using high-voltage sources for the generation of the field. The behaviour of an ER fluid actuator not only depends on the properties of the individual actuator components (ER fluid, energy transducer and energy source) but especially on their combined efforts as a system. Based on a possible scheme for the design of ER fluid actuators, this paper presents important practice-relevant aspects of a systematic actuator construction. Here the behaviour of a commercial ER suspension is examined and compared to a homogeneous ER fluid without yield point using a rotational viscometer and a flow-mode damper realized at the Laboratory of Process Automation (LPA) of the University of Saarland.

  2. R Fluids

    Directory of Open Access Journals (Sweden)

    Caimmi, R.

    2008-06-01

    Full Text Available A theory of collisionless fluids is developed in a unified picture, where nonrotating $(widetilde{Omega_1}=widetilde{Omega_2}= widetilde{Omega_3}=0$ figures with some given random velocity component distributions, and rotating $(widetilde{Omega_1} ewidetilde{Omega_2} e widetilde{Omega_3} $ figures with a different random velocity component distributions, make adjoint configurations to the same system. R fluids are defined as ideal, self-gravitating fluids satisfying the virial theorem assumptions, in presence of systematic rotation around each of the principal axes of inertia. To this aim, mean and rms angular velocities and mean and rms tangential velocity components are expressed, by weighting on the moment of inertia and the mass, respectively. The figure rotation is defined as the mean angular velocity, weighted on the moment of inertia, with respectto a selected axis. The generalized tensor virial equations (Caimmi and Marmo 2005 are formulated for R fluidsand further attention is devoted to axisymmetric configurations where, for selected coordinateaxes, a variation in figure rotation has to be counterbalanced by a variation in anisotropy excess and viceversa. A microscopical analysis of systematic and random motions is performed under a fewgeneral hypotheses, by reversing the sign of tangential or axial velocity components of anassigned fraction of particles, leaving the distribution function and other parametersunchanged (Meza 2002. The application of the reversion process to tangential velocitycomponents is found to imply the conversion of random motion rotation kinetic energy intosystematic motion rotation kinetic energy. The application ofthe reversion process to axial velocity components is found to imply the conversionof random motion translation kinetic energy into systematic motion translation kinetic energy, and theloss related to a change of reference frame is expressed in terms of systematic motion (imaginary rotation kinetic

  3. Inclined layer convection in a colloidal suspension with negative Soret coefficient at large solutal Rayleigh numbers.

    Science.gov (United States)

    Italia, Matteo; Croccolo, Fabrizio; Scheffold, Frank; Vailati, Alberto

    2014-10-01

    Convection in an inclined layer of fluid is affected by the presence of a component of the acceleration of gravity perpendicular to the density gradient that drives the convective motion. In this work we investigate the solutal convection of a colloidal suspension characterized by a negative Soret coefficient. Convection is induced by heating the suspension from above, and at large solutal Rayleigh numbers (of the order of 10(7)-10(8)) convective spoke patterns form. We show that in the presence of a marginal inclination of the cell as small as 19 mrad the isotropy of the spoke pattern is broken and the convective patterns tend to align in the direction of the inclination. At intermediate inclinations of the order of 33 mrad ordered square patterns are obtained, while at inclination of the order of 67 mrad the strong shear flow determined by the inclination gives rise to ascending and descending sheets of fluid aligned parallel to the direction of inclination.

  4. Self-powered suspension criterion and energy regeneration implementation scheme of motor-driven active suspension

    Science.gov (United States)

    Yan, Shuai; Sun, Weichao

    2017-09-01

    Active suspension systems have advantages on mitigating the effects of vehicle vibration caused by road roughness, which are one of the most important component parts in influencing the performances of vehicles. However, high amount of energy consumption restricts the application of active suspension systems. From the point of energy saving, this paper presents a self-powered criterion of the active suspension system to judge whether a motor-driven suspension can be self-powered or not, and then a motor parameter condition is developed as a reference to design a self-powered suspension. An energy regeneration implementation scheme is subsequently proposed to make the active suspension which has the potential to be self-powered achieve energy-saving target in the real application. In this implementation scheme, operating electric circuits are designed based on different working status of the actuator and power source and it is realizable to accumulate energy from road vibration and supply energy to the actuator by switching corresponding electric circuits. To apply the self-powered suspension criterion and energy regeneration implementation scheme, an active suspension system is designed with a constrained H∞ controller and calculation results indicate that it has the capability to be self-powered. Simulation results show that the performances of the self-powered active suspension are nearly the same as those of the active suspension with an external energy source and can achieve energy regeneration at the same time.

  5. Stability of extemporaneously prepared rosuvastatin oral suspension.

    Science.gov (United States)

    Zaid, Abdel Naser; Shtayah, Rania; Qadumi, Ayman; Ghanem, Mashour; Qedan, Rawan; Daibes, Marah; Awwad, Somud Abu; Jaradat, Nidal; Kittana, Naim

    2017-10-01

    The stability of an extemporaneously prepared rosuvastatin suspension stored over 30 days under various storage conditions was evaluated. Rosuvastatin suspension was extemporaneously prepared using commercial rosuvastatin tablets as the source of active pharmaceutical ingredient. The organoleptic properties, dissolution profile, and stability of the formulation were investigated. For the stability studies, samples of the suspension were stored under 2 storage conditions, room temperature (25 °C and 60% relative humidity) and accelerated stability chambers (40 °C and 75% relative humidity). Viscosity, pH, organoleptic properties, and microbial contamination were evaluated according to the approved specifications. High-performance liquid chromatography was used for the analysis and quantification of rosuvastatin in selected samples. Microbiological investigations were also conducted. The prepared suspension showed acceptable organoleptic properties. It showed complete release of rosuvastatin within 15 minutes. The pH of the suspension was 9.8, which remained unchanged during the stability studies. The microbiological investigations demonstrated that the preparation was free of any microbial contamination. In addition, the suspension showed stability within at least the period of use of a 100-mL rosuvastatin bottle. Extemporaneously prepared rosuvastatin 20-mg/mL suspension was stable for 30 days when stored at room temperature. Copyright © 2017 by the American Society of Health-System Pharmacists, Inc. All rights reserved.

  6. Characterization of cell suspensions from solid tumors

    Energy Technology Data Exchange (ETDEWEB)

    Pallavicini, M.

    1985-07-10

    The desirable features of cells in suspension will necessarily be dependent upon the use for which the cells were prepared. Adequate cell yield or recovery is defined by the measurement to be performed. Retention of cellular morphology is important for microscopic identification of cell types in a heterogenous cell suspension, and may be used to determine whether the cells in suspension are representative of those in the tumor in situ. Different dispersal protocols may yield cells with different degrees of clonogenicity, as well as altered biochemical features, such as loss of cellular proteins, surface antigens, nucleotide pools, etc. The quality of the cell suspension can be judged by the degree of cell clumping and level of cellular debris, both of which impact on flow cytometric measurements and studies in which the number of cells be known accurately. Finally, if the data measured on the cells in suspension are to be extrapolated to phenomena occurring in the tumor in situ, it is desirable that the cells in suspension are representative of those in the solid tumor in vivo. This report compares characteristics of tumor cell suspensions obtained by different types of selected disaggregation methods. 33 refs., 2 figs., 4 tabs.

  7. Rheology of nanocrystalline cellulose aqueous suspensions.

    Science.gov (United States)

    Shafiei-Sabet, Sadaf; Hamad, Wadood Y; Hatzikiriakos, Savvas G

    2012-12-11

    The rheological properties and microstructure of nanocrystalline cellulose (NCC) aqueous suspensions have been investigated at different concentrations. The suspension is isotropic up to 3 wt %, and phase separates to liquid crystalline and isotropic domains at higher concentrations where the samples exhibit a fingerprint texture and the viscosity profile shows a three-region behavior, typical of liquid crystals. The suspension behaves as a rheological gel at even higher concentrations where the viscosity profile shows a single shear thinning behavior over the whole range of shear rates investigated. The effects of ultrasound energy and temperature on the rheological properties and structure of these suspensions were studied using polarized optical microscopy and rheometry. Our results indicate that the amount of applied ultrasound energy affects the microstructure of the suspensions and the pitch of the chiral nematic domains. The viscosity profile is changed significantly at low shear rates, whereas the viscosity of biphasic suspensions at intermediate and high shear rates decreased with increasing temperature. This suggests that, between 30 and 40 °C, structural rearrangement takes place. At higher concentrations of about 10 wt %, the temperature has no significant effect on viscosity; however, a marked increase in viscosity has been observed at around 50 °C. Finally, the Cox-Merz rule was found to fail after a critical concentration, thereby implying significant structural formation. This critical concentration is much higher for sonicated compared to unsonicated suspensions.

  8. The Advanced Virgo monolithic fused silica suspension

    Energy Technology Data Exchange (ETDEWEB)

    Aisa, D.; Aisa, S.; Campeggi, C.; Colombini, M. [University of Perugia and INFN Perugia (Italy); Conte, A. [University of Roma Sapienza and INFN Roma (Italy); Farnesini, L. [University of Perugia and INFN Perugia (Italy); Majorana, E.; Mezzani, F. [University of Roma Sapienza and INFN Roma (Italy); Montani, M. [University of Urbino and INFN Firenze (Italy); Naticchioni, L.; Perciballi, M. [University of Roma Sapienza and INFN Roma (Italy); Piergiovanni, F. [University of Urbino and INFN Firenze (Italy); Piluso, A. [University of Perugia and INFN Perugia (Italy); Puppo, P., E-mail: paola.puppo@roma1.infn.it [University of Roma Sapienza and INFN Roma (Italy); Rapagnani, P. [University of Roma Sapienza and INFN Roma (Italy); Travasso, F. [University of Perugia and INFN Perugia (Italy); Vicerè, A. [University of Urbino and INFN Firenze (Italy); Vocca, H. [University of Perugia and INFN Perugia (Italy)

    2016-07-11

    The detection of gravitational waves is one of the most challenging prospects faced by experimental physicists. Suspension thermal noise is an important noise source at operating frequencies between approximately 10 and 30 Hz, and represents a limit to the sensitivity of the ground based interferometric gravitational wave detectors. Its effects can be reduced by minimizing the losses and by optimizing the geometry of the suspension fiber as well as its attachment system. In this proceeding we will describe the mirrors double stage monolithic suspension system to be used in the Advanced Virgo (AdV) detector. We also present the results of the thermal noise study, performed with the help of a finite elements model, taking into account the precise geometry of the fibers attachment systems on the suspension elements. We shall demonstrate the suitability of this suspension for installation in AdV. - Highlights: • Suspension system design for the test masses of the gravitational wave detectors. • Finite element model studies. • Suspension thermal noise studies.

  9. Fluid Shifts

    Science.gov (United States)

    Stenger, M. B.; Hargens, A. R.; Dulchavsky, S. A.; Arbeille, P.; Danielson, R. W.; Ebert, D. J.; Garcia, K. M.; Johnston, S. L.; Laurie, S. S.; Lee, S. M. C.; Liu, J.; Macias, B.; Martin, D. S.; Minkoff, L.; Ploutz-Snyder, R.; Ribeiro, L. C.; Sargsyan, A.; Smith, S. M.

    2017-01-01

    Introduction. NASA's Human Research Program is focused on addressing health risks associated with long-duration missions on the International Space Station (ISS) and future exploration-class missions beyond low Earth orbit. Visual acuity changes observed after short-duration missions were largely transient, but now more than 50 percent of ISS astronauts have experienced more profound, chronic changes with objective structural findings such as optic disc edema, globe flattening and choroidal folds. These structural and functional changes are referred to as the visual impairment and intracranial pressure (VIIP) syndrome. Development of VIIP symptoms may be related to elevated intracranial pressure (ICP) secondary to spaceflight-induced cephalad fluid shifts, but this hypothesis has not been tested. The purpose of this study is to characterize fluid distribution and compartmentalization associated with long-duration spaceflight and to determine if a relation exists with vision changes and other elements of the VIIP syndrome. We also seek to determine whether the magnitude of fluid shifts during spaceflight, as well as any VIIP-related effects of those shifts, are predicted by the crewmember's pre-flight status and responses to acute hemodynamic manipulations, specifically posture changes and lower body negative pressure. Methods. We will examine a variety of physiologic variables in 10 long-duration ISS crewmembers using the test conditions and timeline presented in the figure below. Measures include: (1) fluid compartmentalization (total body water by D2O, extracellular fluid by NaBr, intracellular fluid by calculation, plasma volume by CO rebreathe, interstitial fluid by calculation); (2) forehead/eyelids, tibia, and calcaneus tissue thickness (by ultrasound); (3) vascular dimensions by ultrasound (jugular veins, cerebral and carotid arteries, vertebral arteries and veins, portal vein); (4) vascular dynamics by MRI (head/neck blood flow, cerebrospinal fluid

  10. An attempt to categorize yield stress fluid behaviour

    NARCIS (Netherlands)

    Moller, P.; Fall, A.; Chikkadi, V.; Derks, D.; Bonn, D.

    2009-01-01

    We propose a new view on yield stress materials. Dense suspensions and many other materials have a yield stress—they flow only if a large enough shear stress is exerted on them. There has been an ongoing debate in the literature on whether true yield stress fluids exist, and even whether the concept

  11. Entropy Generation Analysis for a CNT Suspension Nanofluid in Plumb Ducts with Peristalsis

    OpenAIRE

    Noreen Sher Akbar

    2015-01-01

    The purpose of the current investigation was to discuss the entropy generation analysis for a carbon nanotube (CNT) suspension nanofluid in a plumb duct with peristalsis. The entropy generation number due to heat transfer and fluid friction is formulated. The velocity and temperature distributions across the tube are presented along with pressure attributes. Exact analytical solution for velocity and temperature profile are obtained. It is found that the entropy generation number attains high...

  12. Brownian Dynamics of a Suspension of Particles with Constrained Voronoi Cell Volumes

    KAUST Repository

    Singh, John P.

    2015-06-23

    © 2015 American Chemical Society. Solvent-free polymer-grafted nanoparticle fluids consist of inorganic core particles fluidized by polymers tethered to their surfaces. The attachment of the suspending fluid to the particle surface creates a strong penalty for local variations in the fluid volume surrounding the particles. As a model of such a suspension we perform Brownian dynamics of an equilibrium system consisting of hard spheres which experience a many-particle potential proportional to the variance of the Voronoi volumes surrounding each particle (E = α(Vi-V0)2). The coefficient of proportionality α can be varied such that pure hard sphere dynamics is recovered as α → 0, while an incompressible array of hairy particles is obtained as α →. As α is increased the distribution of Voronoi volumes becomes narrower, the mean coordination number of the particle increases and the variance in the number of nearest neighbors decreases. The nearest neighbor peaks in the pair distribution function are suppressed and shifted to larger radial separations as the constraint acts to maintain relatively uniform interstitial regions. The structure factor of the model suspension satisfies S(k=0) → 0 as α → in accordance with expectation for a single component (particle plus tethered fluid) incompressible system. The tracer diffusivity of the particles is reduced by the volume constraint and goes to zero at φ 0.52, indicating an earlier glass transition than has been observed in hard sphere suspensions. The total pressure of the suspension grows in proportion to (αkBT)1/2 as the strength of the volume-constraint potential grows. This stress arises primarily from the interparticle potential forces, while the hard-sphere collisional contribution to the stress is suppressed by the volume constraint.

  13. Brownian Dynamics of a Suspension of Particles with Constrained Voronoi Cell Volumes.

    Science.gov (United States)

    Singh, John P; Walsh, Stuart D C; Koch, Donald L

    2015-06-23

    Solvent-free polymer-grafted nanoparticle fluids consist of inorganic core particles fluidized by polymers tethered to their surfaces. The attachment of the suspending fluid to the particle surface creates a strong penalty for local variations in the fluid volume surrounding the particles. As a model of such a suspension we perform Brownian dynamics of an equilibrium system consisting of hard spheres which experience a many-particle potential proportional to the variance of the Voronoi volumes surrounding each particle (E = α(Vi-V0)(2)). The coefficient of proportionality α can be varied such that pure hard sphere dynamics is recovered as α → 0, while an incompressible array of hairy particles is obtained as α → ∞. As α is increased the distribution of Voronoi volumes becomes narrower, the mean coordination number of the particle increases and the variance in the number of nearest neighbors decreases. The nearest neighbor peaks in the pair distribution function are suppressed and shifted to larger radial separations as the constraint acts to maintain relatively uniform interstitial regions. The structure factor of the model suspension satisfies S(k=0) → 0 as α → ∞ in accordance with expectation for a single component (particle plus tethered fluid) incompressible system. The tracer diffusivity of the particles is reduced by the volume constraint and goes to zero at ϕ ∼ 0.52, indicating an earlier glass transition than has been observed in hard sphere suspensions. The total pressure of the suspension grows in proportion to (αkBT)(1/2) as the strength of the volume-constraint potential grows. This stress arises primarily from the interparticle potential forces, while the hard-sphere collisional contribution to the stress is suppressed by the volume constraint.

  14. Vehicle lateral dynamics stabilization using active suspension

    Directory of Open Access Journals (Sweden)

    Drobný V.

    2008-12-01

    Full Text Available The paper deals with the investigation of active nonlinear suspension control in order to stabilize the lateral vehicle motion in similar way as systems like ESP do. The lateral stabilization of vehicle based on braking forces can be alternatively provided by the different setting of suspension forces. The basis of this control is the nonlinear property of the tyres. The vehicle has at least four wheels and it gives one or more redundant vertical forces that can be used for the different distribution of vertical suspension forces in such a way that resulting lateral and/or longitudinal forces create the required correction moment for lateral dynamic vehicle stabilization.

  15. SLIDING MODE CONTROL FOR ACTIVE AUTOMOBILE SUSPENSIONS

    Institute of Scientific and Technical Information of China (English)

    1998-01-01

    Nonlinear control methods are presented based on theory of sliding mode control (SMC) or variable structure control (VSC) for application to active automobile suspensions. Requirements of reducing manufacturing cost and energy consumption of the active suspension system may be satisfiedby reasonable design of the sliding surface and hydraulic servo system. Emphasis is placed on the study of the discrete sliding mode control method (DSMC) applicable for a new sort of speed on-off solenoid valves of anti-dust capability and low price. Robustness and effectiveness of the feedback linearized controller in typical road conditions are demonstrated by numerical results fora quarter-car suspension model.

  16. Cell Suspension Culture of Neem Tree

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    The establishment of suspension culture system for neem (Azadirachta indica A. Juss) cells and the suspension culture condition was studied. It shows that the neem cell suspension culture system was best in B5 liquid medium, 2.0~4.0mg/L NAA with direct spill method. Based on the integrated analysis of cell biomass, Azadirachtin content and productivity, the optimum culture conditions were B5 liquid medium, 2.0-4.0 mg/L NAA, 3% sucrose at 25 ℃. The optimum rotating speed of the shaker and broth content d...

  17. Large Eddy Simulation for Plunge Breaker and Sediment Suspension

    Institute of Scientific and Technical Information of China (English)

    BAI Yuchuan(白玉川); C.O.NG

    2002-01-01

    Breaking waves are a powerful agent for generating turbulence that plays an important role in many fluid dynamicalprocesses, particularly in the mixing of materials. Breaking waves can dislodge sediment and throw it into suspension,which will then be carried by wave-induced steady current and tidal flow. In order to investigate sediment suspension bybreaking waves, a numerical model based on large-eddy-simulation (LES) is developed. This numerical model can beused to simulate wave breaking and sediment suspension. The model consists of a free-surface model using the surfacemarker method combined with a two-dimensional model that solves the flow equations. The turbulence and the turbulentdiffusion are described by a large-eddy-simulation (LES) method where the large turbulence features are simulated bysolving the flow equations, and a subgrid model represents the small-scale turbulence that is not resolved by the flowmodel. A dynamic eddy viscosity subgrid scale stress model has been used for the present simulation. By applying thismodel to Stokes' wave breaking problem in the surf zone, we find that the model results agree very well with experimentaldata. By use of this model to simulation of the breaking process of a periodic wave, it can be found that the model canreproduce the complicated flow phenomena, especially the plunging breaker. It reflects the dynamic structures of roller orvortex in the plunging breaker, and when the wave breaks, many strong vortex structures will be produced in the innersurf zone where the concentration of suspended sediment can thereby become relatively high.

  18. A vibration energy harvesting system based on a pulse fluid flow transducer and its tests%基于脉冲液流换能器的振动能量回收原理与实验研究

    Institute of Scientific and Technical Information of China (English)

    袁四美; 廖昌荣; 赵丹侠; 刘琼; 韩亮

    2013-01-01

    To solve the energy supply problem of a self-powered Magneto-rheological damping modulator system, a vibration energy harvesting system based on a pulse fluid flow transducer was presented. Through a conversion of vibration energy-fluid flow energy-mechanical energy-electrical energy, vibration energy harvesting was realized. An analysis model of a pulse fluid flow transducer composed of a gear motor, a flywheel and a permanent magnet generator was built. The output voltage, power conversion and conversion efficiency of the pulse fluid flow transducer were simulated via Matlab software under the condition of sinusoideal excitation. In order to verify the rationality of the theoretical analysis, a vibration energy harvesting system based on the pulse fluid flow transducer was designed and fabricated. The vibration energy harvesting system was tested with a J95-I type shock absorber test-table. Under the sinusoidal excitation condition, the theoretical voltage characteristics of the transducer were compared with those from tests, and the theoretical efficiencies were compared with the test ones. It was shown that the puls-fluid flow transducer can relize vibration energy harvesting; the energy conversion efficiency reaches 48.65% and the average output power reaches 37.4 watt under the condition of 30 ohm load.%针对自供电磁流变阻尼调节系统的能量供给问题,提出基于脉冲液流换能器的振动能量回收方法,通过振动能-液流能-机械能-电能的变换,实现振动能量回收.建立了基于齿轮马达、飞轮和永磁发动机的脉冲液流换能器分析模型,利用Matlab软件对正弦振动下换能器的电压输出特性、功率转换特性和转换效率进行仿真.为验证理论分析的正确性,设计制作了基于脉冲液流换能器的振动能量回收装置,利用J95-Ⅰ减振器测试台上对振动能量回收装置实验测试,比较了正弦激励条件下换能器的理论电压特性与实测电压特性

  19. Enhanced diffusion of tracer particles in dilute bacterial suspensions.

    Science.gov (United States)

    Morozov, Alexander; Marenduzzo, Davide

    2014-04-28

    Swimming bacteria create long-range velocity fields that stir a large volume of fluid and move around passive particles dispersed in the fluid. Recent experiments and simulations have shown that long-time mean-squared displacement of passive particles in a bath of swimming bacteria exhibits diffusive behaviour with an effective diffusion coefficient significantly larger than its thermal counterpart. A comprehensive theoretical prediction of this effective diffusion coefficient and the understanding of the enhancement mechanism remain a challenge. Here, we adapt the kinetic theory by Lin et al., J. Fluid Mech., 2011, 669, 167 developed for 'squirmers' to the bacterial case to quantitatively predict enhanced diffusivity of tracer particles in dilute two- and three-dimensional suspensions of swimming bacteria. We demonstrate that the effective diffusion coefficient is a product of the bacterial number density, their swimming speed, a geometric factor characterising the velocity field created by a single bacterium, and a numerical factor. We show that the numerical factor is, in fact, a rather strong function of the system parameters, most notably the run length of the bacteria, and that these dependencies have to be taken into account to quantitatively predict the enhanced diffusivity. We perform molecular-dynamics-type simulations to confirm the conclusions of the kinetic theory. Our results are in good agreement with the values of enhanced diffusivity measured in recent two- and three-dimensional experiments.

  20. Effect of acid and temperature on the discontinuous shear thickening phenomenon of silica nanoparticle suspensions

    Science.gov (United States)

    Li, Shuangbing; Wang, Jixiao; Cai, Wei; Zhao, Song; Wang, Zhi; Wang, Shichang

    2016-08-01

    The discontinuous shear thickening (DST) phenomenon of silica nanoparticle suspensions was investigated in this article. First, the non-aggregated silica nanoparticles were synthesized and characterized. The results indicate that the silica nanoparticles are spherical particles with a narrow size distribution with a diameter of approximately 90 nm. Next, the influence of nitric acid concentration and temperature on the DST phenomenon of shear thickening fluids (STFs) was investigated. The results indicate that the concentrated fluids with nitric acid concentration below 8.50 mmol/L and at a temperature below 40 °C exhibit a readily noticeable DST phenomenon.

  1. Reducing Viscosity of Liquid Suspensions by pulsed electric or magnetic field

    Science.gov (United States)

    Tao, R.

    2007-03-01

    Viscosity of liquid suspensions is of great importance. Controlling the viscosity is vital in science and engineering. In electrorheological (ER) or magentorheological (MR) fluids, electric or magnetic field is used to increase the viscosity. However, in most cases we need to lower the viscosity. For example, reducing blood's viscosity improves circulation and prevents cardiovascular events. Lowering the viscosity of crude oil is the key to transporting offshore oil via undersea pipelines. Unfortunately, to date there are no effective methods for reducing the viscosity except by changing the temperature. In case that changing temperature is not an option, such as in the above examples, reducing the viscosity becomes formidable. Here we present a theory and experimental results showing that application of a suitable electric or magnetic field pulse can significantly reduce the viscosity of liquid suspensions for several hours with no change of temperature. The field induces dipolar interactions between the suspended particles and forces them to aggregate into large particles. The aggregation changes the rheological properties of the fluids and reduces the effective viscosity. Positive experimental results with MR fluids and crude oil indicate that this method, developed from the basic mechanism of viscosity, is universal and powerful for all liquid suspensions with broad applications.

  2. Temperature dependent rheological property of copper oxide nanoparticles suspension (nanofluid).

    Science.gov (United States)

    Kulkarni, Devdatta P; Das, Debendra K; Chukwu, Godwin A

    2006-04-01

    A nanofluid is the dispersion of metallic solid particles of nanometer size in a base fluid such as water or ethylene glycol. The presence of these nanoparticles affects the physical properties of a nanofluid via various factors including shear stress, particle loading, and temperature. In this paper the rheological behavior of copper oxide (CuO) nanoparticles of 29 nm average diameter dispersed in deionized (DI) water is investigated over a range of volumetric solids concentrations of 5 to 15% and various temperatures varying from 278-323 degrees K. These experiments showed that these nanofluids exhibited time-independent pseudoplastic and shear-thinning behavior. The suspension viscosities of nanofluids decrease exponentially with respect to the shear rate. Suspension viscosity follows the correlation in the form ln(mus) = A(1/T)-B, where constants A and B are the functions of volumetric concentrations. The calculated viscosities from the developed correlations and experimental values were found to be within +/- 10% of their values.

  3. Swimming in a suspension of rod-like molecules

    Science.gov (United States)

    Shi, Juan; Powers, Thomas

    2016-11-01

    In nature, it is common for microorganisms to swim in fluids with microstructure, such as mucus. Motivated by this fact, there have been many recent theoretical, computational, and experimental studies of idealized swimmers in a dilute solution of flexible polymers. Here we study this problem from a different point of view by considering swimmers in a dilute solution of rigid rod-like polymers. We study the prescribed swimming problem of Taylor's sheet in a dilute suspension of non-Brownian rods. Using a simple continuum constitutive law for the suspension that describes the stress in terms of velocity gradient and local rod orientation, we calculate swimming speed to second order in the amplitude of the wave. Due to stresses induced by the presence of the rods, the first-order flow field differs from that of the Newtonian case. We find that the swimming speed increases linearly with rod concentration: the presence of the rods always makes the swimmer go faster. We also consider the problem of a finite swimmer by studying a two-dimensional circular squirmer. The squirmer is defined as a circle with a prescribed tangential slip velocity that leads to propulsion. By varying the prescribed slip boundary condition, we study both pushers and pullers.

  4. Characterisation of electrorheological liquids based on suspensions; Charakterisierung von elektrorheologischen Fluessigkeiten auf Basis von Suspensionen

    Energy Technology Data Exchange (ETDEWEB)

    Johnston, Lucien [FLUDICON GmbH, Darmstadt (Germany); Schneider, Steffen; Schneider, Ines [Wehrwissenschaftliches Institut fuer Werk-, Explosiv- und Betriebsstoffe (WIWEB), Erding (Germany)

    2008-08-15

    Electrorheological fluids (ERF) belong to the group of 'Smart Materials'. These suspensions have the favourable property of changing their viscosity in an electrical field. This change is spontaneous (response time under 1 ms), continuously variable (from a thin fluid to a semi-solid state), reversible and can be repeated as often as desired. ER-fluids also have certain sensory properties. The sum of these properties allows for the design of mechanical valves which have no moving components. Instead of adjusting the cross-sectional area of a valve orifice, variations in pressure drop over the valve are realised by altering the viscosity of the fluid itself. The simplicity and effectiveness of the ER-effect has lead to a diverse range of applications which make use of this property - from continuously variable hydraulic shock absorbers to highly dynamic actuators. Since the discovery of the ER-effect in the 1904s, many ER-fluids have been developed and tested. This article will discuss the properties and composition of an industrially successful ER-suspension as well as highlighting its implementation in a diverse range of engineering applications. (orig.)

  5. 21 CFR 1404.740 - Are suspension proceedings formal?

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 9 2010-04-01 2010-04-01 false Are suspension proceedings formal? 1404.740 Section 1404.740 Food and Drugs OFFICE OF NATIONAL DRUG CONTROL POLICY GOVERNMENTWIDE DEBARMENT AND SUSPENSION (NONPROCUREMENT) Suspension § 1404.740 Are suspension proceedings formal? (a)...

  6. 13 CFR 120.660 - Suspension or revocation.

    Science.gov (United States)

    2010-01-01

    ... 13 Business Credit and Assistance 1 2010-01-01 2010-01-01 false Suspension or revocation. 120.660... Market Suspension Or Revocation of Participant in Secondary Market § 120.660 Suspension or revocation. (a) Suspension or revocation of Lender, broker, dealer, or Registered Holder for violation of Secondary...

  7. 39 CFR 954.6 - Revocation or suspension.

    Science.gov (United States)

    2010-07-01

    ... 39 Postal Service 1 2010-07-01 2010-07-01 false Revocation or suspension. 954.6 Section 954.6... DENIAL, SUSPENSION, OR REVOCATION OF PERIODICALS MAIL PRIVILEGES § 954.6 Revocation or suspension. When... privileges, he or she shall issue a ruling of suspension or revocation to the publisher at the last...

  8. 45 CFR 1641.13 - Causes for suspension.

    Science.gov (United States)

    2010-10-01

    ... 45 Public Welfare 4 2010-10-01 2010-10-01 false Causes for suspension. 1641.13 Section 1641.13..., SUSPENSION AND REMOVAL OF RECIPIENT AUDITORS Suspension § 1641.13 Causes for suspension. The debarring... that: (a) A cause for debarment under § 1641.7 may exist; (b) The IPA has been indicted for...

  9. On the behaviour of gelled fibre suspensions in steady shear

    Energy Technology Data Exchange (ETDEWEB)

    Wolf, Bettina [Unilever Corporate Research, Bedford (United Kingdom); University of Nottingham, Division of Food Sciences, Loughborough (United Kingdom); White, Duncan; Melrose, John R.; Frith, William J. [Unilever Corporate Research, Bedford (United Kingdom)

    2007-03-15

    The shear rheological properties of suspensions of gelled agar fibres in a low viscosity Newtonian matrix fluid were investigated. Two classes of fibres, low aspect ratio fibres and high aspect ratio fibres with an aspect ratio of the order of 10 and 100 respectively were included in the investigations. For all fibre phase volumes investigated, from as low as 0.01 upwards, the flow curves are characterised by an apparent yield stress followed by shear-thinning which was independent of the fibre aspect ratio. Based on our analysis of the flow curves, we conclude that the high aspect ratio fibres behave like flexible threads in contrast to the low aspect ratio fibres whose high shear relative viscosity is successfully described by a relation for long rigid rods. These findings are supported by flow visualisation using an optical shearing stage coupled to a light microscope. (orig.)

  10. Convective flows of colloidal suspension in an inclined closed cell

    Science.gov (United States)

    Smorodin, Boris; Cherepanov, Ivan; Ishutov, Sergey

    2016-12-01

    The nonlinear spatiotemporal evolution of convective flows is numerically investigated in the case of colloidal suspension filling an inclined closed cell heated from below. The bifurcation diagram (the dependency of the Nusselt number on the Rayleigh number) is obtained. The characteristics of the wave and steady patterns are investigated depending on heat intensity. The travelling wave changing travel direction and the non-regular oscillatory flow are found to be stable solutions within a certain interval of the Rayleigh number. Temporal Fourier decomposition is used together with other diagnostic tools to analyse the complex bifurcation and spatiotemporal properties caused by the interplay of the gravity-induced gradient of concentration and convective mixing of the fluid. It is shown that a more complex flow structure exists at a lower heating intensity (Rayleigh number).

  11. Transiently Jammed State in Shear Thickening Suspensions under Shear

    Science.gov (United States)

    Mukhopadhyay, Shomeek; Allen, Benjamin; Brown, Eric

    2014-03-01

    We examine the response of a suspension of cornstarch and water under normal impact at controlled velocities. This is a model system to understand why a person can run on the surface of a discontinuous shear thickening fluid. Using simultaneous high-speed imaging of the top and bottom surfaces along with normal force measurements allows us to investigate whether the force response is a result of system spanning structures. We observe a shear thickening transition where above a critical velocity the normal force increases by orders of magnitude. In the high force regime the force response is displacement dependent like a solid rather than velocity dependent like a liquid. The stresses are on the order of 106 Pa which is enough to hold up a person's weight. In this regime imaging shows the existence of a solid like structure that extends to the bottom interface.

  12. 49 CFR 570.8 - Suspension systems.

    Science.gov (United States)

    2010-10-01

    ... down on one end of vehicle and release. Note number of cycles of free rocking motion. Repeat procedure at other end of vehicle. ...) Inspection procedure. Examine front and rear end suspension parts for conditions indicated. (b) Shock...

  13. Experimental Evaluation of Mountain Bike Suspension Systems

    Directory of Open Access Journals (Sweden)

    J. Titlestad

    2003-01-01

    Full Text Available A significant distinction between competitive mountain bikes is whether they have a suspension system. Research studies indicate that a suspension system gives advantages, but it is difficult to quantify the benefits because they depend on so many variables, including the physiology and psychology of the cyclist, the roughness of the track and the design of the suspension system. A laboratory based test rig has been built that allows the number of variables in the system to be reduced and test conditions to be controlled. The test rig simulates regular impacts of the rear wheel with bumps in a rolling road. The physiological variables of oxygen consumption and heart rate were measured, together with speeds and forces at various points in the system. Physiological and mechanical test results both confirm a significant benefit in using a suspension system on the simulated rough track, with oxygen consumption reduced by around 30 % and power transmitted through the pedals reduced by 30 % to 60 %.

  14. Numerical Study of Suspension Plasma Spraying

    CERN Document Server

    Farrokhpanah, Amirsaman; Mostaghimi, Javad

    2016-01-01

    A numerical study of suspension plasma spraying (SPS) is presented in the current work. The liquid suspension jet is replaced with a train of droplets containing the suspension particles injected into the plasma flow. Atomization, evaporation, and melting of different components are considered for particles as they travel towards the substrate. Effect of different parameters on particle conditions during flight and upon impact on the substrate are investigated. Initially, influence of the torch operating conditions such as inlet flow rate and power are studied. Additionally, effect of injector parameters like injection location, flow rate, and angle are examined. The model used in current study takes high temperature gradients and non-continuum effects into account. Moreover, the important effect of change in physical properties of suspension droplets as a result of evaporation is included in the model. These mainly include variations in heat transfer properties and viscosity. Utilizing this improved model, s...

  15. Piezo-actuated Vibration and Flutter Control

    OpenAIRE

    S.B. Kandagal; Kartik Venkatraman

    2006-01-01

    The potential application of smart materials is being investigated by various researchers inthe perspective of building intelligent systems. A smart structure consists of distributed actuatorsand sensors with associated processors to analyse and control the structure. Piezoceramics,magnetostrictive materials, electro-rheological fluids, magneto-rheological fluids, shape memoryalloys, fibre optics are quite often used in realising a smart/intelligent system. In this paper,vibration and flutter...

  16. Impact of Ohio Administrative License Suspension*

    OpenAIRE

    Voas, Robert B.; Tippetts, A. Scott; Taylor, Eileen P.

    1998-01-01

    This report covers an analysis of the driving records of Ohio’s 45,788 drivers who were convicted of driving under the influence (DUI) between July 1, 1990, and August 30, 1995, to determine the specific deterrent impact of the Ohio administrative license suspension (ALS**) law on DUI recidivism. Our data support the conclusion that, under the ALS law, license suspensions were earlier and more certain. Consequently, the number of drunk-driving convictions, moving offenses, and crashes of firs...

  17. The suspension of disbelief in videogames

    OpenAIRE

    Brown, Douglas; William

    2012-01-01

    This thesis was submitted for the degree of Doctor of Philosophy and was awarded by Brunel University This thesis explores the ways in which suspension of disbelief works in digital games. Primarily concerned with how players relate imaginatively to the often major dissonance between gameplay and narrative in digital games, this thesis questions how the literate players of games reconcile these complex texts imaginatively. Proposing that Samuel Taylor Coleridge's concept of suspension of d...

  18. Damping of roll vibrations of vehicle suspension

    Science.gov (United States)

    Le, K. C.; Pieper, A.

    2014-04-01

    Small forced vibrations of an axle model of independent suspensions having four degrees of freedom are studied. The exact analytical solution of the generalised Lagrange equation enables one to produce 3D plots of the normalised amplitudes of forced vibrations versus frequency and excitation ratio or phase difference of the road inputs. The analysis of these plots exhibits some deficiency in damping of roll vibrations of conventional vehicle suspensions. The possibilities of improvement are discussed.

  19. Splashing onset in dense suspension droplets

    OpenAIRE

    Peters, Ivo; Xu, Qin; Jaeger, Heinrich M.

    2013-01-01

    We investigate the impact of droplets of dense suspensions onto a solid substrate. We show that a global hydrodynamic balance is unable to predict the splash onset and propose to replace it by an energy balance at the level of the particles in the suspension. We experimentally verify that the resulting, particle-based Weber number gives a reliable, particle size and density dependent splash onset criterion. We further show that the same argument also explains why, in bimodal systems, smaller ...

  20. Fluid dynamics

    CERN Document Server

    Ruban, Anatoly I

    This is the first book in a four-part series designed to give a comprehensive and coherent description of Fluid Dynamics, starting with chapters on classical theory suitable for an introductory undergraduate lecture course, and then progressing through more advanced material up to the level of modern research in the field. The present Part 1 consists of four chapters. Chapter 1 begins with a discussion of Continuum Hypothesis, which is followed by an introduction to macroscopic functions, the velocity vector, pressure, density, and enthalpy. We then analyse the forces acting inside a fluid, and deduce the Navier-Stokes equations for incompressible and compressible fluids in Cartesian and curvilinear coordinates. In Chapter 2 we study the properties of a number of flows that are presented by the so-called exact solutions of the Navier-Stokes equations, including the Couette flow between two parallel plates, Hagen-Poiseuille flow through a pipe, and Karman flow above an infinite rotating disk. Chapter 3 is d...

  1. Robust Sliding Mode Fuzzy Control of a Car Suspension System

    OpenAIRE

    Ayman A. Aly

    2013-01-01

    Different characteristics can be considered in a suspension system design like: ride comfort, body travel, road handling and suspension travel. No suspension system can optimize all these parameters together but a better tradeoff among these parameters can be achieved in active suspension system.Objective of this paper is to establish a robust control technique of the active suspension system for a quarter-car model. The paper describes also the model and controller used in the study and dis...

  2. Magnelok technology: a complement to magnetorheological fluids

    Science.gov (United States)

    Carlson, J. David

    2004-07-01

    Magnetorheological or MR fluids have been successfully used to enable highly effective semi-active control systems in automobile primary suspensions to control unwanted motions in civil engineering structures and to provide force-feedback in steer-by-wire systems. A key to the successful use of MR fluids is an appreciation and understanding of the balance and trade-off between the magnetically controlled on-state force and the ever-present off-state viscous force. In all MR fluid applications, one must deal with the fact that MR fluids never fully decouple or go to zero force in their off-state. Magnelok devices are a magnetically controlled compliment to traditional MR fluid devices that have been developed to enable a true force decoupling in the off-state. Magnelok devices may be embodied as linear or rotary dampers, brakes, lockable struts or position holding devices. They are particularly suitable for lock/un-lock applications. Unlike MR fluid devices they contain no fluid yet they do provide a variable level of friction damping that is controlled by the magnitude of the applied magnetic field. Magnelok devices are low cost as they easily accommodate relatively loose mechanical tolerances and require no seals or accumulator. A variety of controllable Magnelok devices and applications are described.

  3. Formulation and Validation of an Efficient Computational Model for a Dilute, Settling Suspension Undergoing Rotational Mixing

    Energy Technology Data Exchange (ETDEWEB)

    Sprague, Michael A.; Stickel, Jonathan J.; Sitaraman, Hariswaran; Crawford, Nathan C.; Fischer, Paul F.

    2017-04-11

    Designing processing equipment for the mixing of settling suspensions is a challenging problem. Achieving low-cost mixing is especially difficult for the application of slowly reacting suspended solids because the cost of impeller power consumption becomes quite high due to the long reaction times (batch mode) or due to large-volume reactors (continuous mode). Further, the usual scale-up metrics for mixing, e.g., constant tip speed and constant power per volume, do not apply well for mixing of suspensions. As an alternative, computational fluid dynamics (CFD) can be useful for analyzing mixing at multiple scales and determining appropriate mixer designs and operating parameters. We developed a mixture model to describe the hydrodynamics of a settling cellulose suspension. The suspension motion is represented as a single velocity field in a computationally efficient Eulerian framework. The solids are represented by a scalar volume-fraction field that undergoes transport due to particle diffusion, settling, fluid advection, and shear stress. A settling model and a viscosity model, both functions of volume fraction, were selected to fit experimental settling and viscosity data, respectively. Simulations were performed with the open-source Nek5000 CFD program, which is based on the high-order spectral-finite-element method. Simulations were performed for the cellulose suspension undergoing mixing in a laboratory-scale vane mixer. The settled-bed heights predicted by the simulations were in semi-quantitative agreement with experimental observations. Further, the simulation results were in quantitative agreement with experimentally obtained torque and mixing-rate data, including a characteristic torque bifurcation. In future work, we plan to couple this CFD model with a reaction-kinetics model for the enzymatic digestion of cellulose, allowing us to predict enzymatic digestion performance for various mixing intensities and novel reactor designs.

  4. Studying mixing in Non-Newtonian blue maize flour suspensions using color analysis.

    Science.gov (United States)

    Trujillo-de Santiago, Grissel; Rojas-de Gante, Cecilia; García-Lara, Silverio; Ballescá-Estrada, Adriana; Alvarez, Mario Moisés

    2014-01-01

    Non-Newtonian fluids occur in many relevant flow and mixing scenarios at the lab and industrial scale. The addition of acid or basic solutions to a non-Newtonian fluid is not an infrequent operation, particularly in Biotechnology applications where the pH of Non-Newtonian culture broths is usually regulated using this strategy. We conducted mixing experiments in agitated vessels using Non-Newtonian blue maize flour suspensions. Acid or basic pulses were injected to reveal mixing patterns and flow structures and to follow their time evolution. No foreign pH indicator was used as blue maize flours naturally contain anthocyanins that act as a native, wide spectrum, pH indicator. We describe a novel method to quantitate mixedness and mixing evolution through Dynamic Color Analysis (DCA) in this system. Color readings corresponding to different times and locations within the mixing vessel were taken with a digital camera (or a colorimeter) and translated to the CIELab scale of colors. We use distances in the Lab space, a 3D color space, between a particular mixing state and the final mixing point to characterize segregation/mixing in the system. Blue maize suspensions represent an adequate and flexible model to study mixing (and fluid mechanics in general) in Non-Newtonian suspensions using acid/base tracer injections. Simple strategies based on the evaluation of color distances in the CIELab space (or other scales such as HSB) can be adapted to characterize mixedness and mixing evolution in experiments using blue maize suspensions.

  5. Studying mixing in Non-Newtonian blue maize flour suspensions using color analysis.

    Directory of Open Access Journals (Sweden)

    Grissel Trujillo-de Santiago

    Full Text Available BACKGROUND: Non-Newtonian fluids occur in many relevant flow and mixing scenarios at the lab and industrial scale. The addition of acid or basic solutions to a non-Newtonian fluid is not an infrequent operation, particularly in Biotechnology applications where the pH of Non-Newtonian culture broths is usually regulated using this strategy. METHODOLOGY AND FINDINGS: We conducted mixing experiments in agitated vessels using Non-Newtonian blue maize flour suspensions. Acid or basic pulses were injected to reveal mixing patterns and flow structures and to follow their time evolution. No foreign pH indicator was used as blue maize flours naturally contain anthocyanins that act as a native, wide spectrum, pH indicator. We describe a novel method to quantitate mixedness and mixing evolution through Dynamic Color Analysis (DCA in this system. Color readings corresponding to different times and locations within the mixing vessel were taken with a digital camera (or a colorimeter and translated to the CIELab scale of colors. We use distances in the Lab space, a 3D color space, between a particular mixing state and the final mixing point to characterize segregation/mixing in the system. CONCLUSION AND RELEVANCE: Blue maize suspensions represent an adequate and flexible model to study mixing (and fluid mechanics in general in Non-Newtonian suspensions using acid/base tracer injections. Simple strategies based on the evaluation of color distances in the CIELab space (or other scales such as HSB can be adapted to characterize mixedness and mixing evolution in experiments using blue maize suspensions.

  6. Pleural Fluid Analysis Test

    Science.gov (United States)

    ... Home Visit Global Sites Search Help? Pleural Fluid Analysis Share this page: Was this page helpful? Formal name: Pleural Fluid Analysis Related tests: Pericardial Fluid Analysis , Peritoneal Fluid Analysis , ...

  7. Rheological behavior of oxide nanopowder suspensions

    Science.gov (United States)

    Cinar, Simge

    Ceramic nanopowders offer great potential in advanced ceramic materials and many other technologically important applications. Because a material's rheological properties are crucial for most processing routes, control of the rheological behavior has drawn significant attention in the recent past. The control of rheological behavior relies on an understanding of how different parameters affect the suspension viscosities. Even though the suspension stabilization mechanisms are relatively well understood for sub-micron and micron size particle systems, this knowledge cannot be directly transferred to nanopowder suspensions. Nanopowder suspensions exhibit unexpectedly high viscosities that cannot be explained with conventional mechanisms and are still a topic of investigation. This dissertation aims to establish the critical parameters governing the rheological behavior of concentrated oxide nanopowder suspensions, and to elucidate the mechanisms by which these parameters control the rheology of these suspensions. Aqueous alumina nanopowders were chosen as a model system, and the findings were extrapolated to other oxide nanopowder systems such as zirconia, yttria stabilized zirconia, and titania. Processing additives such as fructose, NaCl, HCl, NaOH, and ascorbic acid were used in this study. The effect of solids content and addition of fructose on the viscosity of alumina nanopowder suspensions was investigated by low temperature differential scanning calorimetry (LT-DSC), rheological, and zeta potential measurements. The analysis of bound water events observed in LT-DSC revealed useful information regarding the rheological behavior of nanopowder suspensions. Because of the significance of interparticle interactions in nanopowder suspensions, the electrostatic stabilization was investigated using indifferent and potential determining ions. Different mechanisms, e.g., the effect of the change in effective volume fraction caused by fructose addition and electrostatic

  8. Configuration design and accuracy analysis of a novel magneto rheological finishing machine tool for concave surfaces with small radius of curvature

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Henan; Chen, Mingjun [Harbin Institute of Technology, Harbin (China); Yu, Bo; Zhen, Fang [China Electronics Technology Group Corporation No.26 Research Institute, Chongqing (China)

    2016-07-15

    Magnetorheological finishing (MRF) is a computer-controlled deterministic polishing technique that is widely used in the production of high-quality optics. In order to overcome the defects of existing MRF processes that are unable to achieve concave surfaces with small radius of curvature, a configuration method of a novel structured MRF machine tool using small ball-end permanent-magnet polishing head is proposed in this paper. The preliminary design focuses on the structural configuration of the machine, which includes the machine body, motion units and accessory equipment, and so on. Structural deformation and fabrication accuracy of the machine are analyzed theoretically, in which the reasonable structure sizes, manufacturing errors and assembly errors of main structural components are given for configuration optimization. Based on the theoretical analysis, a four-axes linkage MRF machine tool is developed. Preliminary experiments of spot polishing are carried out and the results indicate that the proposed MRF process can achieve stable polishing area which meets requirement of deterministic polishing. A typical small-bore complex component is polished on the developed device and fine surface quality is obtained with sphericity of the finished spherical surfaces 1.3 μm and surface roughness Ra less than 0.018 μm.

  9. On-off skyhook semi-active control via a magneto-rheological (MR) damper for airfoil-based energy harvesting systems

    Science.gov (United States)

    Pang, J. N. I.; Harno, H. G.; Lee, V. C. C.

    2017-07-01

    An on-off skyhook semi-active control strategy via MR damper is proposed in this study to enhance the performance of a two degree-of-freedom (DOF) airfoil-based energy harvester. For simplicity, only the plunge mode of the airfoil model is examined. NACA0012 airfoil is selected as the vibrating body where energy is harvested and converted into electricity via piezoelectric transduction. Behavioural performance of an actual MR damper is represented numerically with MATLAB/SIMULINK blocks of a conventional Bouc-Wen model. Simulation of the airfoil model is also performed on MATLAB to acquire its dynamic responses. A comparison between passive and semi-actively controlled airfoil systems demonstrates that the proposed strategy is superior in three different aspects - versatility, energy harvesting and sustaining structural integrity.

  10. Pitched Blade Turbine Efficiency at Particle Suspension

    Directory of Open Access Journals (Sweden)

    D. Ceres

    2010-01-01

    Full Text Available Mixing suspensions is a very important hydraulic operation. The pitched six-blade turbine is a widely-used axial-flow impeller. This paper deals with effect relative impeller size and particle content on theefficiency of a pitched six-blade turbine at particle suspension. Two pitched six-blade turbines were used in model measurements of just suspension impeller speed. The ratios of the vessel to agitator diameter D/d were 3 and 4.5. The measurements were carried out in a dish-bottomed vessel 300 mm in diameter. The just suspension impeller speeds were measured using an electrochemical method, and were checked visually. A 2.5 % NaCl water solution was used as the liquid phase, and glass particles with four equivalent diameters between 0.18 and 0.89 mmand volumetric concentration from 2.5 % to 40% were usedasthesolid phase. The criterion values πs=Po√Fr'3(d/D7 were calculated from the particle suspension and power consumption measurements. The dependencies of πs on particle content cv show that larger agitators are more efficient for higher particle content.

  11. Phase transitions of pyrogenic silica suspensions: a comparison to model laponite.

    Science.gov (United States)

    Kätzel, Uwe; Richter, Thomas; Stintz, Michael; Barthel, Herbert; Gottschalk-Gaudig, Torsten

    2007-09-01

    Pyrogenic silica is often used as a thickening agent in paints, pastes, adhesives, or resins. Other applications include, e.g., abrasives in chemical mechanical planarization in the microelectronics industry. In all these applications it is essential to control the state of dispersion. Sometimes, phase transitions from the liquid to the solid state are required while in other cases they have to be completely avoided for the whole shelf life. The nature and influencing parameters of the fluid-solid transition for pyrogenic silica have not been investigated so far. Most investigations deal with the phase transitions of small clay particles such as laponite. Here, we dedicate our interest to the behavior of pyrogenic silica suspensions with varying specific surface area and ionic background concentration. To get an impression of the phase transition behavior we compare our results to model laponite suspensions. We apply dynamic light scattering measurements in the backscattering regime to minimize multiple scattering contributions from concentrated pyrogenic silica suspensions. Further on we exert a decomposition of the measured autocorrelation functions into an ergodic and nonergodic contribution. The analysis of the ergodic spectrum yields two different gelation kinetics for both systems, laponite and pyrogenic silica. For laponite these are in accordance with earlier investigations. The kinetics depend on the ionic background and the solids content of the suspensions. Additionally, we used dynamic extinction spectroscopy to follow the phase transitions of pyrogenic silica on a macroscale.

  12. Colloidal behavior of aqueous montmorillonite suspensions in the presence of non-ionic polymer

    Science.gov (United States)

    Gareche, M.; Azri, N.; Allal, A.; Zeraibi, N.

    2015-04-01

    In this paper we characterized at first, the rheological behavior of the bentonite suspensions and the aqueous solutions of polyethylene oxide (PEO), then we were investigated the influence of this polymer in a water-based drilling fluid model (6% of bentonite suspension). The objective is to exhibit how the non ionic polymer with molecular weight 6×103 g/mol. of varying concentration mass (0.7%, 1%, 2% et 3%) significantly alter the rheological properties (yield stress, viscosity, loss and elastic modulus) of the bentonite suspensions. The rheological measurements made in simple shear and in dynamic on the mixture (water-bentonite-PEO), showed rheological properties of bentonite suspensions both in the presence and absence of non-ionic polymer. The PEO presents an affinity for the bentonite particles slowing down their kinetic aggregation. The analysis by X-rays diffraction also allowed understanding the structure of this mixture. It had revealed the intercalation between of the clay platelets on one hand, and the links bridges assured by the chains of polymer between bentonite particles beyond a critical concentration in PEO on the other hand. The Herschel- Bulkley rheological model is used for the correlation of our experimental results.

  13. Depletion forces induce visco-elasto-capillary thinning of non-Brownian suspensions

    Science.gov (United States)

    Harich, R.; Deblais, A.; Colin, A.; Kellay, H.

    2016-06-01

    Droplet pinch-off, which occurs when a drop of liquid detaches from a capillary, can be strongly modified in the presence of complex fluids such as polymer solutions and suspensions giving rise to long and slender filaments that thin slowly in time. While for polymers, the molecular conformations of the molecules in the filament are responsible for such a behavior, in suspensions the mechanisms at play remain to be deciphered. Here we show, experimentally, that while liquid bridges of non-Brownian suspensions of moderate concentrations have a thinning behavior very close to that of the solvent, the addition of short-chain polymers inducing depletion attractions between the particles in the suspension changes the thinning dynamics and gives rise to exponential thinning in time. The characteristic time of this dynamics increases with polymer concentration and therefore the intensity of the depletion forces at play. The tunability of this dynamics may be important for injket and 3D printing applications where short rupture times are sought for or in other situations where drop formation has to be minimized or inhibited.

  14. Flagellum synchronization inhibits large-scale hydrodynamic instabilities in sperm suspensions

    Science.gov (United States)

    Schöller, Simon F.; Keaveny, Eric E.

    2016-11-01

    Sperm in suspension can exhibit large-scale collective motion and form coherent structures. Our picture of such coherent motion is largely based on reduced models that treat the swimmers as self-locomoting rigid bodies that interact via steady dipolar flow fields. Swimming sperm, however, have many more degrees of freedom due to elasticity, have a more exotic shape, and generate spatially-complex, time-dependent flow fields. While these complexities are known to lead to phenomena such as flagellum synchronization and attraction, how these effects impact the overall suspension behaviour and coherent structure formation is largely unknown. Using a computational model that captures both flagellum beating and elasticity, we simulate suspensions on the order of 103 individual swimming sperm cells whose motion is coupled through the surrounding Stokesian fluid. We find that the tendency for flagella to synchronize and sperm to aggregate inhibits the emergence of the large-scale hydrodynamic instabilities often associated with active suspensions. However, when synchronization is repressed by adding noise in the flagellum actuation mechanism, the picture changes and the structures that resemble large-scale vortices appear to re-emerge. Supported by an Imperial College PhD scholarship.

  15. Symmetry breaking of particle trajectories due to magnetic interactions in a dilute suspension

    Energy Technology Data Exchange (ETDEWEB)

    Cunha, F.R., E-mail: frcunha@unb.br [Vortex Laboratory of Fluid Mechanics of Complex Flows and Departamento de Engenharia Mecanica, Faculdade de Tecnologia, Universidade de Brasilia, Campus Universitario Darcy Ribeiro, 70910-900 Brasilia, DF (Brazil); Gontijo, R.G., E-mail: rafaelgabler@gmail.com [Vortex Laboratory of Fluid Mechanics of Complex Flows and Departamento de Engenharia Mecanica, Faculdade de Tecnologia, Universidade de Brasilia, Campus Universitario Darcy Ribeiro, 70910-900 Brasilia, DF (Brazil); Sobral, Y.D., E-mail: ydsobral@unb.br [Vortex Laboratory of Fluid Mechanics of Complex Flows and Departamento de Matematica, Instituto de Ciencias Exatas, Universidade de Brasilia, Campus Universitario Darcy Ribeiro, 70910-900 Brasilia, DF (Brazil)

    2013-01-15

    This work presents a numerical study of the relative trajectories of two magnetic particles interacting in a dilute suspension. The suspension is composed of magnetic spherical particles of different radius and density immersed in a Newtonian fluid. The particles settle relative to one another under the action of gravity and, when in close proximity, exert on each other magnetic force and torque due to their permanent magnetization. The equations of motion for both translation and rotation of the particles are solved and particle inertia is included in the calculation. The numerical simulations are based on the direct computations of the hydrodynamic and of the magnetic interactions between the rigid particles in the regime of non-zero Stokes number. A detailed study of the relative trajectories of two magnetic particles in a dilute suspension allows us to explore irreversible interactions that lead to particle aggregation and particle migration induced by the breaking of the time reversibility of the creeping flow due to magnetic effects. The calculation shows that the rotation of the particles produced by magnetic interactions change significantly the dynamics of collisions of magnetic particle. - Highlights: Black-Right-Pointing-Pointer Relative trajectories of magnetic particles. Black-Right-Pointing-Pointer Magnetic interactions of particles under a gravity field. Black-Right-Pointing-Pointer Magnetic interactions break relative trajectories reversibility. Black-Right-Pointing-Pointer Particle Rotation decrease the rate of aggregation. Black-Right-Pointing-Pointer Dispersion in a magnetic suspension due to magnetic interactions.

  16. Robust Sliding Mode Fuzzy Control of a Car Suspension System

    Directory of Open Access Journals (Sweden)

    Ayman A. Aly

    2013-07-01

    Full Text Available Different characteristics can be considered in a suspension system design like: ride comfort, body travel, road handling and suspension travel. No suspension system can optimize all these parameters together but a better tradeoff among these parameters can be achieved in active suspension system.Objective of this paper is to establish a robust control technique of the active suspension system for a quarter-car model. The paper describes also the model and controller used in the study and discusses the vehicle response results obtained from a range of road input simulations. A comparison of robust suspension sliding fuzzy control and passive control is shown using MATLAB simulations.

  17. A review of dynamics modelling of friction wedge suspensions

    Science.gov (United States)

    Wu, Qing; Cole, Colin; Spiryagin, Maksym; Sun, Yan Quan

    2014-11-01

    Three-piece bogies with friction wedge suspensions are the most widely used bogies in heavy haul trains. Fiction wedge suspensions play a key role in these wagon systems. This article reviews current techniques in dynamic modelling of friction wedge suspension with various motivations: to improve dynamic models of friction wedge suspensions so as to improve general wagon dynamics simulations; to seek better friction wedge suspension models for wagon stability assessments in complex train systems; to improve the modelling of other friction devices, such as friction draft gear. Relevant theories and friction wedge suspension models developed by using commercial simulation packages and in-house simulation packages are reviewed.

  18. Fouling of thin-channel and tubular membrane modules by dilute suspensions

    Energy Technology Data Exchange (ETDEWEB)

    Ilias, S.; Govind, R.

    1988-10-01

    In this paper, fouling of thin-channel and tubular ultrafiltration (UF) membrane modules by dilute suspensions have been studied theoretically. A hydrodynamic analysis of fluid-particle system is presented to describe the role of dilute suspensions in fouling such membrane modules. The present analysis assumes that for very dilute suspensions, only inertial effects are important for particulate fouling. Particle trajectory history and hence the fouling is computed from equations of motion for the particles, where the fluid-flow is given by the full solution of Navier-Stokes equation. To simulate the flux decline due to build up of foulant layer on the membrane walls, it is assumed that the deposition of particles on the membrane surface at discrete time interval is a steady state event and thus formulating the fouling problem as an infinite series of successive steady state events. Present simulation results indicate that inertial effects are important and under positive wall permeation flux conditions, particles are encouraged to migrate towards the membrane wall causing so-called membrane fouling by the particulates.

  19. Drying of suspension and pastes in fluidized bed of inert particles

    Directory of Open Access Journals (Sweden)

    ZORANA LJ. ARSENIJEVIC

    2000-12-01

    Full Text Available A fluid bed dryer with inert particles was used for the drying of suspensions and pastes. The effects of the operating conditions on the dryer throughput and on the product quality were investigated. Experiments were performed in a cylindrical column 215 mm in diameter and 1200 mm in height with 0.925 mm diameter glass spheres as the fluidizing media. Cineb fungicide, copper hydroxide and pure water were used as the feed material. With respect to the main efficiency criteria, i.e., specific water evaporation rate, specific heat consumption and specific air consumption, a fluid bed dryer with inert particles represents a very attractive alternative to other drying technologies. A high drying efficiency results from the large contact area and from the large temperature difference between the inlet and outlet air. A rapid mixing of the particles, due to aggregative fluidization and mechanical agitation, leads to nearly isothermal conditions throughout the bed. In our experiments, suspensions and very dense pastes were successfully treated. Suspension and product hold-up in the bed varies between 6 and 8 % by mass and a product with the same particle size as the raw material is obtained.

  20. Flux-Feedback Magnetic-Suspension Actuator

    Science.gov (United States)

    Groom, Nelson J.

    1990-01-01

    Flux-feedback magnetic-suspension actuator provides magnetic suspension and control forces having linear transfer characteristics between force command and force output over large range of gaps. Hall-effect devices used as sensors for electronic feedback circuit controlling currents flowing in electromagnetic windings to maintain flux linking suspended element at substantially constant value independent of changes in length of gap. Technique provides effective method for maintenance of constant flux density in gap and simpler than previous methods. Applications include magnetic actuators for control of shapes and figures of antennas and of precise segmented reflectors, magnetic suspensions in devices for storage of angular momentum and/or kinetic energy, and systems for control, pointing, and isolation of instruments.